https://medservatory.com/ 2026-11-19T09:00:00.000Z weekly 1 https://medservatory.com/lessons 2026-11-19T09:00:00.000Z weekly 0.8 https://medservatory.com/notes 2026-11-19T09:00:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1 2026-11-15T10:45:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/systems/cardiovascular 2026-11-12T18:30:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/renal-urinary 2026-11-08T06:00:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/respiratory 2026-11-15T03:05:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/gastrointestinal 2026-11-15T10:45:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/endocrine 2026-11-15T08:05:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/nervous-behavioural 2026-11-15T04:25:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/haem-onc 2026-11-15T09:15:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/immunology 2026-11-15T05:35:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/pharmacology 2026-11-15T06:55:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/systems/microbiology 2026-11-15T10:25:00.000Z weekly 0.7 https://medservatory.com/usmle-step-1/renal-acid-base 2026-11-02T05:35:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/renal-physiology 2026-11-08T06:00:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/cardiovascular 2026-11-11T06:30:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg 2026-11-12T18:30:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/respiratory-physiology 2026-11-15T03:05:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/neuroanatomy-localisation 2026-11-15T04:25:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/immunology 2026-11-15T05:35:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic 2026-11-15T06:55:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/endocrinology 2026-11-15T08:05:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/haematology-oncology 2026-11-15T09:15:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/microbiology 2026-11-15T10:25:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/gi-physiology-pathology 2026-11-15T10:45:00.000Z weekly 0.8 https://medservatory.com/usmle-step-2-ck 2026-10-24T20:30:00.000Z weekly 0.8 https://medservatory.com/usmle-step-2-ck/specialties/emergency-medicine 2026-10-24T20:30:00.000Z weekly 0.7 https://medservatory.com/usmle-step-2-ck/emergency-medicine 2026-10-24T20:30:00.000Z weekly 0.8 https://medservatory.com/usmle-step-1/cardiovascular/pressure-volume-loop https://medservatory.com/thumbs/pressure-volume-loop.png Pressure-Volume Loop Explained: The Four Phases and Valve Events | USMLE Step 1 https://medservatory.com/thumbs/pressure-volume-loop.png The pressure-volume loop explained: the four phases, the valve event at each corner, why it runs anticlockwise, and how to read SV, EF and stroke work. https://www.youtube-nocookie.com/embed/pnirdeOYxqM 300 2026-10-23T17:30:00+01:00 2026-10-23T16:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/preload-pressure-volume-loop https://medservatory.com/thumbs/preload-pressure-volume-loop.png Preload on the Pressure-Volume Loop: EDV, Stroke Volume and the EDPVR | USMLE Step 1 https://medservatory.com/thumbs/preload-pressure-volume-loop.png How preload changes the pressure-volume loop: the EDPVR and ESPVR, why more filling raises EDV and stroke volume while ESV barely moves, and what lowers it. https://www.youtube-nocookie.com/embed/3saOW2YKKbU 304 2026-10-23T21:30:00+01:00 2026-10-23T20:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/afterload-pressure-volume-loop https://medservatory.com/thumbs/afterload-pressure-volume-loop.png Afterload on the Pressure-Volume Loop: Why Higher Afterload Shrinks Stroke Volume | USMLE Step 1 https://medservatory.com/thumbs/afterload-pressure-volume-loop.png Afterload on the pressure-volume loop: draw the arterial elastance (Ea) line and predict how higher or lower afterload changes ESV, stroke volume and EF. https://www.youtube-nocookie.com/embed/9B097579Fo4 289 2026-10-24T01:30:00+01:00 2026-10-24T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/contractility-espvr https://medservatory.com/thumbs/contractility-espvr.png Contractility on the Pressure-Volume Loop: ESPVR Explained | USMLE Step 1 https://medservatory.com/thumbs/contractility-espvr.png Contractility on the pressure-volume loop: how inotropy rotates the ESPVR, and what that does to end-systolic volume, stroke volume and ejection fraction. https://www.youtube-nocookie.com/embed/wKUOC3E-HKM 317 2026-10-24T05:30:00+01:00 2026-10-24T04:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/wiggers-diagram-cardiac-cycle https://medservatory.com/thumbs/wiggers-diagram-cardiac-cycle.png USMLE Step 1 | Wiggers Diagram Explained: The Cardiac Cycle Step by Step https://medservatory.com/thumbs/wiggers-diagram-cardiac-cycle.png Wiggers diagram explained: follow pressures, volume, heart sounds and the ECG through the seven phases of the cardiac cycle, and see why each valve moves. https://www.youtube-nocookie.com/embed/srhVXjVTuc4 330 2026-11-08T12:30:00+00:00 2026-11-08T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/frank-starling-curve https://medservatory.com/thumbs/frank-starling-curve.png USMLE Step 1 | Frank-Starling Curve Explained: Preload, Inotropy and Heart Failure https://medservatory.com/thumbs/frank-starling-curve.png The Frank-Starling curve explained: why more filling raises stroke volume, and how inotropy and systolic heart failure shift the curve. USMLE Step 1. https://www.youtube-nocookie.com/embed/Y8gyvkOc2i0 284 2026-11-08T18:30:00+00:00 2026-11-08T18:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/aortic-stenosis-vs-mitral-regurgitation-pv-loop https://medservatory.com/thumbs/aortic-stenosis-vs-mitral-regurgitation-pv-loop.png USMLE Step 1 | Aortic Stenosis vs Mitral Regurgitation on the Pressure-Volume Loop https://medservatory.com/thumbs/aortic-stenosis-vs-mitral-regurgitation-pv-loop.png Aortic stenosis vs mitral regurgitation on the pressure-volume loop: tall and narrow vs wide and shifted right, and why the wide loop overstates forward flow. https://www.youtube-nocookie.com/embed/sYU2DA074OM 341 2026-11-09T00:30:00+00:00 2026-11-09T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/cardiac-output-fick-principle https://medservatory.com/thumbs/cardiac-output-fick-principle.png USMLE Step 1 | Cardiac Output and the Fick Principle Explained https://medservatory.com/thumbs/cardiac-output-fick-principle.png Fick principle explained: cardiac output = oxygen consumption ÷ arteriovenous oxygen content difference. Worked example, sampling sites and the mL/dL trap. https://www.youtube-nocookie.com/embed/DcrditRnmc0 307 2026-11-09T06:30:00+00:00 2026-11-09T06:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/hfref-vs-hfpef-pressure-volume-loop https://medservatory.com/thumbs/hfref-vs-hfpef-pressure-volume-loop.png USMLE Step 1 | HFrEF vs HFpEF Explained: Pressure-Volume Loops, ESPVR and EDPVR https://medservatory.com/thumbs/hfref-vs-hfpef-pressure-volume-loop.png HFrEF vs HFpEF on the pressure-volume loop: a flatter ESPVR (EF 40% or less) versus a stiffer EDPVR (EF 50% or more), and why both raise filling pressure. https://www.youtube-nocookie.com/embed/IaCV7pHiaMA 333 2026-11-09T12:30:00+00:00 2026-11-09T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/poiseuille-law-vascular-resistance https://medservatory.com/thumbs/poiseuille-law-vascular-resistance.png USMLE Step 1 | Poiseuille's Law and Resistance: Why Arterioles Control Blood Pressure https://medservatory.com/thumbs/poiseuille-law-vascular-resistance.png Poiseuille's law explained: resistance falls with radius to the fourth power, so arterioles set MAP = CO × TPR. Series vs parallel resistance and a question. https://www.youtube-nocookie.com/embed/dX6DIUcXkoM 315 2026-11-09T18:30:00+00:00 2026-11-09T18:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/venous-return-cardiac-function-curve https://medservatory.com/thumbs/venous-return-cardiac-function-curve.png USMLE Step 1 | Venous Return and Cardiac Function Curves Explained https://medservatory.com/thumbs/venous-return-cardiac-function-curve.png Venous return and cardiac function curves: the crossing point sets cardiac output and right atrial pressure. See how volume, venous tone and inotropy shift it. https://www.youtube-nocookie.com/embed/HtAWtkoEBGA 311 2026-11-10T00:30:00+00:00 2026-11-10T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/baroreceptor-reflex https://medservatory.com/thumbs/baroreceptor-reflex.png USMLE Step 1 | The Baroreceptor Reflex Explained: Carotid Sinus, Standing and Haemorrhage https://medservatory.com/thumbs/baroreceptor-reflex.png The baroreceptor reflex explained: carotid sinus (CN IX), aortic arch (CN X), NTS, then vagal and sympathetic output. Predict standing, bleeding, massage. https://www.youtube-nocookie.com/embed/RMN91G428IQ 317 2026-11-10T06:30:00+00:00 2026-11-10T06:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/myocardial-oxygen-supply-demand https://medservatory.com/thumbs/myocardial-oxygen-supply-demand.png USMLE Step 1 | Myocardial Oxygen Supply and Demand: Why Tachycardia Causes Ischaemia https://medservatory.com/thumbs/myocardial-oxygen-supply-demand.png Myocardial oxygen supply and demand: the three drivers of demand, why left coronary flow is mainly diastolic, and why tachycardia causes ischaemia. https://www.youtube-nocookie.com/embed/PN_PxcCXNe4 290 2026-11-10T12:30:00+00:00 2026-11-10T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/unstable-angina-nstemi-stemi-acs https://medservatory.com/thumbs/unstable-angina-nstemi-stemi-acs.png USMLE Step 1 | From Plaque to Acute Coronary Syndrome: Unstable Angina vs NSTEMI vs STEMI https://medservatory.com/thumbs/unstable-angina-nstemi-stemi-acs.png Unstable angina vs NSTEMI vs STEMI: how plaque rupture or erosion forms a coronary clot, and how clot size, troponin and ST elevation sort ACS. https://www.youtube-nocookie.com/embed/hvoewT5VFZ4 290 2026-11-10T18:30:00+00:00 2026-11-10T18:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/anti-ischemic-drugs-nitrates-beta-blockers-ccb https://medservatory.com/thumbs/anti-ischemic-drugs-nitrates-beta-blockers-ccb.png USMLE Step 1 | Anti-Ischaemic Drugs: Nitrates, Beta Blockers and Calcium Channel Blockers https://medservatory.com/thumbs/anti-ischemic-drugs-nitrates-beta-blockers-ccb.png Anti-ischaemic drugs explained: how nitrates, beta blockers and calcium channel blockers lower oxygen demand and change heart rate, preload and afterload. https://www.youtube-nocookie.com/embed/Njv0xkkyAik 296 2026-11-11T00:30:00+00:00 2026-11-11T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/cardiovascular/complications-of-myocardial-infarction-timeline https://medservatory.com/thumbs/complications-of-myocardial-infarction-timeline.png USMLE Step 1 | Complications of Myocardial Infarction by Timeline: Rupture, Dressler, Aneurysm https://medservatory.com/thumbs/complications-of-myocardial-infarction-timeline.png Complications of myocardial infarction by timeline: match arrhythmia, pericarditis, papillary, septal and free wall rupture, aneurysm and Dressler to the wall. https://www.youtube-nocookie.com/embed/DnJocEc38xk 299 2026-11-11T06:30:00+00:00 2026-11-11T06:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/hypothalamic-pituitary-axes-and-feedback https://medservatory.com/thumbs/hypothalamic-pituitary-axes-and-feedback.png USMLE Step 1 | Hypothalamic-Pituitary Axes: Primary, Secondary and Tertiary Disorders https://medservatory.com/thumbs/hypothalamic-pituitary-axes-and-feedback.png Hypothalamic-pituitary axes explained: the three-step chain, negative feedback, and how to predict hormone levels in primary, secondary and tertiary disorders. https://www.youtube-nocookie.com/embed/miRlH5wMJQI 305 2026-11-15T07:00:00+00:00 2026-11-15T07:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/primary-vs-secondary-endocrine-disorders https://medservatory.com/thumbs/primary-vs-secondary-endocrine-disorders.png USMLE Step 1 | Primary vs Secondary Endocrine Disorders: How to Read Paired Hormone Levels https://medservatory.com/thumbs/primary-vs-secondary-endocrine-disorders.png Primary vs secondary endocrine disorders: read the target hormone, then the trophic hormone. Opposite means primary; the same direction means secondary. https://www.youtube-nocookie.com/embed/dFvNNWd7Pdo 313 2026-11-15T07:05:00+00:00 2026-11-15T07:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/insulin-secretion-beta-cell https://medservatory.com/thumbs/insulin-secretion-beta-cell.png USMLE Step 1 | Insulin Secretion in the Beta Cell: KATP Channel and Sulfonylureas https://medservatory.com/thumbs/insulin-secretion-beta-cell.png Insulin secretion in the beta cell, step by step: glucose, glucokinase, ATP, KATP channel closure, Ca²⁺ entry and exocytosis, plus how sulfonylureas act. https://www.youtube-nocookie.com/embed/30adDov-Oxo 306 2026-11-15T07:10:00+00:00 2026-11-15T07:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/insulin-vs-glucagon-signalling https://medservatory.com/thumbs/insulin-vs-glucagon-signalling.png USMLE Step 1 | Insulin vs Glucagon Signalling: Receptors and Effects in Liver, Muscle and Fat https://medservatory.com/thumbs/insulin-vs-glucagon-signalling.png Insulin vs glucagon explained for USMLE Step 1: tyrosine kinase and Akt versus Gs and cAMP, and what each hormone does in liver, muscle and fat. https://www.youtube-nocookie.com/embed/UJSkfhcD7Ow 319 2026-11-15T07:15:00+00:00 2026-11-15T07:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/dka-vs-hhs-pathophysiology https://medservatory.com/thumbs/dka-vs-hhs-pathophysiology.png USMLE Step 1 | DKA vs HHS Pathophysiology: Insulin Deficiency, Ketones and Hyperosmolality https://medservatory.com/thumbs/dka-vs-hhs-pathophysiology.png DKA vs HHS pathophysiology: why insulin lack causes ketoacidosis, why residual insulin in HHS holds back ketones, and how to calculate effective osmolality. https://www.youtube-nocookie.com/embed/frgnbdzaYsY 358 2026-11-15T07:20:00+00:00 2026-11-15T07:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/diabetes-drugs-by-mechanism https://medservatory.com/thumbs/diabetes-drugs-by-mechanism.png USMLE Step 1 | Diabetes Drugs by Mechanism: Metformin, Sulfonylureas, GLP-1, SGLT2 and Insulin https://medservatory.com/thumbs/diabetes-drugs-by-mechanism.png Diabetes drugs by mechanism: sort metformin, sulfonylureas, GLP-1, DPP-4, SGLT2 inhibitors, TZDs and insulin by site of action and signature side effect. https://www.youtube-nocookie.com/embed/u7i3_GPv-vs 358 2026-11-15T07:25:00+00:00 2026-11-15T07:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/thyroid-hormone-synthesis-and-drug-targets https://medservatory.com/thumbs/thyroid-hormone-synthesis-and-drug-targets.png USMLE Step 1 | Thyroid Hormone Synthesis: Iodide Trapping, TPO and the Drugs That Block Each Step https://medservatory.com/thumbs/thyroid-hormone-synthesis-and-drug-targets.png Thyroid hormone synthesis step by step: iodide trapping, pendrin, TPO organification, coupling, release and T₄ to T₃ conversion, and the drugs that block them. https://www.youtube-nocookie.com/embed/Ylml4eOo0wk 314 2026-11-15T07:30:00+00:00 2026-11-15T07:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/calcium-homeostasis-pth-vitamin-d-and-calcitonin https://medservatory.com/thumbs/calcium-homeostasis-pth-vitamin-d-and-calcitonin.png USMLE Step 1 | Calcium Homeostasis: PTH, Vitamin D and Calcitonin Explained https://medservatory.com/thumbs/calcium-homeostasis-pth-vitamin-d-and-calcitonin.png Calcium homeostasis explained: how PTH, vitamin D and calcitonin steer calcium and phosphate across bone, kidney and gut, with the albumin correction. https://www.youtube-nocookie.com/embed/x3k1GOi2Q38 328 2026-11-15T07:35:00+00:00 2026-11-15T07:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/adrenal-steroidogenesis https://medservatory.com/thumbs/adrenal-steroidogenesis.png USMLE Step 1 | Adrenal Steroidogenesis: Zones, Enzymes, Aldosterone, Cortisol, Androgens https://medservatory.com/thumbs/adrenal-steroidogenesis.png Adrenal steroidogenesis by zone and enzyme: how cholesterol becomes aldosterone, cortisol and androgens, and why 17α-hydroxylase is the fork in the pathway. https://www.youtube-nocookie.com/embed/tAXDSOfCd2Q 329 2026-11-15T07:40:00+00:00 2026-11-15T07:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/congenital-adrenal-hyperplasia https://medservatory.com/thumbs/congenital-adrenal-hyperplasia.png USMLE Step 1 | CAH: 21-Hydroxylase vs 11-Beta vs 17-Alpha Deficiency https://medservatory.com/thumbs/congenital-adrenal-hyperplasia.png Congenital adrenal hyperplasia explained: ask what piles up, what falls and where it spills to predict blood pressure, potassium and androgens for each enzyme. https://www.youtube-nocookie.com/embed/g-ctuaD6lJ8 344 2026-11-15T07:45:00+00:00 2026-11-15T07:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/cushing-syndrome-dexamethasone-suppression-acth https://medservatory.com/thumbs/cushing-syndrome-dexamethasone-suppression-acth.png USMLE Step 1 | Cushing Syndrome Explained: Dexamethasone Suppression Test and ACTH https://medservatory.com/thumbs/cushing-syndrome-dexamethasone-suppression-acth.png Cushing syndrome for USMLE Step 1: screening tests, the dexamethasone suppression test and ACTH, and how to localise the source: pituitary, ectopic or adrenal. https://www.youtube-nocookie.com/embed/i3B6_m98ifc 329 2026-11-15T07:50:00+00:00 2026-11-15T07:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/primary-hyperaldosteronism https://medservatory.com/thumbs/primary-hyperaldosteronism.png USMLE Step 1 | Primary Hyperaldosteronism: High Aldosterone, Low Renin, Metabolic Alkalosis https://medservatory.com/thumbs/primary-hyperaldosteronism.png Primary hyperaldosteronism for USMLE Step 1: why aldosterone causes hypertension, hypokalaemia and alkalosis, why renin falls, and how the ratio screens. https://www.youtube-nocookie.com/embed/GpHdQDmAwBg 327 2026-11-15T07:55:00+00:00 2026-11-15T07:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/siadh-vs-diabetes-insipidus https://medservatory.com/thumbs/siadh-vs-diabetes-insipidus.png USMLE Step 1 | SIADH vs Diabetes Insipidus: Central vs Nephrogenic DI and the Desmopressin Test https://medservatory.com/thumbs/siadh-vs-diabetes-insipidus.png SIADH vs diabetes insipidus explained: use serum sodium, urine osmolality and the desmopressin response to separate central from nephrogenic DI. https://www.youtube-nocookie.com/embed/T__Y0nFEuJM 344 2026-11-15T08:00:00+00:00 2026-11-15T08:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/endocrinology/multiple-endocrine-neoplasia-men1-men2a-men2b https://medservatory.com/thumbs/multiple-endocrine-neoplasia-men1-men2a-men2b.png USMLE Step 1 | MEN1, MEN2A, MEN2B: Genes and Tumours (Multiple Endocrine Neoplasia) https://medservatory.com/thumbs/multiple-endocrine-neoplasia-men1-men2a-men2b.png MEN1, MEN2A and MEN2B explained: menin loss versus activating RET, and each syndrome's tumour combination. Includes a worked example and a practice question. https://www.youtube-nocookie.com/embed/l258n_GpFMs 313 2026-11-15T08:05:00+00:00 2026-11-15T08:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/gi-physiology-pathology/gi-hormones-gastrin-cck-secretin-gip-motilin https://medservatory.com/thumbs/gi-hormones-gastrin-cck-secretin-gip-motilin.png USMLE Step 1 | GI Hormones: Gastrin, CCK, Secretin, GIP and Motilin Explained https://medservatory.com/thumbs/gi-hormones-gastrin-cck-secretin-gip-motilin.png GI hormones explained: match gastrin, CCK, secretin, GIP and motilin to their source cell, stimulus and actions, with the G, I, S, K, M cell lineup for Step 1. https://www.youtube-nocookie.com/embed/znGK2qK5vNU 314 2026-11-15T10:30:00+00:00 2026-11-15T10:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/gi-physiology-pathology/gastric-acid-secretion-parietal-cell https://medservatory.com/thumbs/gastric-acid-secretion-parietal-cell.png USMLE Step 1 | Gastric Acid Secretion Explained: Parietal Cell, PPIs and H2 Blockers https://medservatory.com/thumbs/gastric-acid-secretion-parietal-cell.png Gastric acid secretion explained: how the parietal cell pumps out acid, how acetylcholine, histamine and gastrin drive it, and where PPIs and H₂ blockers act. https://www.youtube-nocookie.com/embed/iQJ4YC8A86A 292 2026-11-15T10:35:00+00:00 2026-11-15T10:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/gi-physiology-pathology/h-pylori-peptic-ulcer-disease-mucosal-defence https://medservatory.com/thumbs/h-pylori-peptic-ulcer-disease-mucosal-defence.png USMLE Step 1 | H. pylori and Peptic Ulcer Disease Explained: NSAIDs, Duodenal vs Gastric Ulcer https://medservatory.com/thumbs/h-pylori-peptic-ulcer-disease-mucosal-defence.png H. pylori and peptic ulcer disease explained: how H. pylori and NSAIDs break mucosal defence, and why antral or body infection gives duodenal or gastric ulcers. https://www.youtube-nocookie.com/embed/XSeb9J5tAoM 314 2026-11-15T10:40:00+00:00 2026-11-15T10:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/gi-physiology-pathology/bilirubin-metabolism-jaundice https://medservatory.com/thumbs/bilirubin-metabolism-jaundice.png USMLE Step 1 | Bilirubin Metabolism and Jaundice: Pre-hepatic, Hepatic, Post-hepatic https://medservatory.com/thumbs/bilirubin-metabolism-jaundice.png Bilirubin metabolism and jaundice: trace haem to urobilinogen, then sort pre-hepatic, hepatic and post-hepatic jaundice by bilirubin type, enzymes and stool. https://www.youtube-nocookie.com/embed/VTmpXYQK2kk 344 2026-11-15T10:45:00+00:00 2026-11-15T10:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/microcytic-anaemia https://medservatory.com/thumbs/microcytic-anaemia.png USMLE Step 1 | Microcytic Anaemia: Iron Deficiency, Inflammation, Sideroblastic, Thalassaemia https://medservatory.com/thumbs/microcytic-anaemia.png Microcytic anaemia explained: sort iron deficiency, inflammation, sideroblastic anaemia and thalassaemia trait using ferritin, iron-binding capacity and HbA₂. https://www.youtube-nocookie.com/embed/UbBJRXpUhRU 337 2026-11-15T08:10:00+00:00 2026-11-15T08:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/iron-deficiency-vs-anaemia-of-inflammation https://medservatory.com/thumbs/iron-deficiency-vs-anaemia-of-inflammation.png USMLE Step 1 | Hepcidin Explained: Iron Deficiency vs Anaemia of Inflammation https://medservatory.com/thumbs/iron-deficiency-vs-anaemia-of-inflammation.png Hepcidin explained: how it shuts ferroportin and traps iron in cells, and how ferritin and iron-binding capacity separate inflammation from iron deficiency https://www.youtube-nocookie.com/embed/_5wOTcyFQ9I 334 2026-11-15T08:15:00+00:00 2026-11-15T08:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/b12-vs-folate-deficiency https://medservatory.com/thumbs/b12-vs-folate-deficiency.png USMLE Step 1 | Vitamin B12 vs Folate Deficiency: MMA, Homocysteine and Neuro Signs https://medservatory.com/thumbs/b12-vs-folate-deficiency.png B12 vs folate deficiency explained: both raise homocysteine and cause megaloblastic anaemia, but only B12 raises methylmalonic acid and damages the nerves. https://www.youtube-nocookie.com/embed/5-m-wnevsqU 323 2026-11-15T08:20:00+00:00 2026-11-15T08:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/intravascular-vs-extravascular-haemolysis https://medservatory.com/thumbs/intravascular-vs-extravascular-haemolysis.png USMLE Step 1 | Intravascular vs Extravascular Hemolysis: Haptoglobin, LDH, Bilirubin and Urine https://medservatory.com/thumbs/intravascular-vs-extravascular-haemolysis.png Intravascular vs extravascular haemolysis: how haptoglobin, LDH, bilirubin and urine findings separate lysis in the vessels from clearance by macrophages. https://www.youtube-nocookie.com/embed/kJ1g08YP9Zw 327 2026-11-15T08:25:00+00:00 2026-11-15T08:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/g6pd-deficiency-vs-hereditary-spherocytosis https://medservatory.com/thumbs/g6pd-deficiency-vs-hereditary-spherocytosis.png USMLE Step 1 | G6PD vs Hereditary Spherocytosis: Heinz Bodies, Bite Cells and EMA Test https://medservatory.com/thumbs/g6pd-deficiency-vs-hereditary-spherocytosis.png G6PD deficiency vs hereditary spherocytosis by mechanism: Heinz bodies and bite cells against spherocytes, a raised MCHC, a negative DAT and low EMA binding. https://www.youtube-nocookie.com/embed/9YzAwzq2dcg 336 2026-11-15T08:30:00+00:00 2026-11-15T08:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/sickle-cell-disease-pathophysiology https://medservatory.com/thumbs/sickle-cell-disease-pathophysiology.png USMLE Step 1 | Sickle Cell Disease Pathophysiology: HbS Polymerisation to Vaso-Occlusion https://medservatory.com/thumbs/sickle-cell-disease-pathophysiology.png Sickle cell disease pathophysiology: how valine for glutamate at position 6 makes HbS polymerise on deoxygenation, and what drives sickling and haemolysis https://www.youtube-nocookie.com/embed/3pBpk68E-B0 326 2026-11-15T08:35:00+00:00 2026-11-15T08:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/primary-haemostasis-platelet-adhesion-and-aggregation https://medservatory.com/thumbs/primary-haemostasis-platelet-adhesion-and-aggregation.png USMLE Step 1 | Primary Haemostasis: Platelet Adhesion, Activation, Aggregation, Antiplatelet Drugs https://medservatory.com/thumbs/primary-haemostasis-platelet-adhesion-and-aggregation.png Primary haemostasis explained: platelet adhesion, activation and aggregation, the antiplatelet drugs that act on each step, and Bernard-Soulier vs Glanzmann. https://www.youtube-nocookie.com/embed/nSYO0KnAVoQ 353 2026-11-15T08:40:00+00:00 2026-11-15T08:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/coagulation-cascade-pt-aptt https://medservatory.com/thumbs/coagulation-cascade-pt-aptt.png USMLE Step 1 | Coagulation Cascade Explained: PT vs aPTT, Extrinsic, Intrinsic and Common Pathways https://medservatory.com/thumbs/coagulation-cascade-pt-aptt.png Coagulation cascade explained: map the extrinsic, intrinsic and common pathways onto PT and aPTT, then predict which test each factor deficiency prolongs. https://www.youtube-nocookie.com/embed/gLCQTRaBxqo 321 2026-11-15T08:45:00+00:00 2026-11-15T08:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/von-willebrand-disease-vs-haemophilia https://medservatory.com/thumbs/von-willebrand-disease-vs-haemophilia.png USMLE Step 1 | Von Willebrand Disease vs Haemophilia: Bleeding Time, PTT and Factor Levels https://medservatory.com/thumbs/von-willebrand-disease-vs-haemophilia.png Von Willebrand disease vs haemophilia: tell them apart by bleeding pattern, bleeding time, PTT and factor levels, using the two jobs of von Willebrand factor. https://www.youtube-nocookie.com/embed/l6-DiNB7x-A 332 2026-11-15T08:50:00+00:00 2026-11-15T08:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/anticoagulants-heparin-warfarin-doacs https://medservatory.com/thumbs/anticoagulants-heparin-warfarin-doacs.png USMLE Step 1 | Anticoagulants Explained: Heparin, Warfarin, DOACs, Monitoring and Reversal Agents https://medservatory.com/thumbs/anticoagulants-heparin-warfarin-doacs.png Anticoagulants explained for USMLE Step 1: the target, monitoring test and reversal agent of heparin, warfarin, dabigatran and the factor Xa blockers. https://www.youtube-nocookie.com/embed/qMqDc9JlJ5Q 334 2026-11-15T08:55:00+00:00 2026-11-15T08:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/heparin-induced-thrombocytopenia https://medservatory.com/thumbs/heparin-induced-thrombocytopenia.png USMLE Step 1 | Heparin-Induced Thrombocytopenia (HIT): PF4 Antibodies, 4Ts and Why It Clots https://medservatory.com/thumbs/heparin-induced-thrombocytopenia.png Heparin-induced thrombocytopenia explained: the PF4–heparin antibody, why platelets fall yet clots form, the 4Ts score, the tests and treatment. USMLE Step 1. https://www.youtube-nocookie.com/embed/LqOyZaC1Fko 329 2026-11-15T09:00:00+00:00 2026-11-15T09:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/dic-vs-ttp-vs-hus https://medservatory.com/thumbs/dic-vs-ttp-vs-hus.png USMLE Step 1 | DIC vs TTP vs HUS: Mechanism, PT/PTT and ADAMTS13 https://medservatory.com/thumbs/dic-vs-ttp-vs-hus.png DIC vs TTP vs HUS: tell them apart by what forms the clot and by the PT and PTT, ADAMTS13 and fibrinogen. Includes a worked TTP example and a practice question. https://www.youtube-nocookie.com/embed/L7M6onw41_o 333 2026-11-15T09:05:00+00:00 2026-11-15T09:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/aml-vs-all-vs-cml-vs-cll https://medservatory.com/thumbs/aml-vs-all-vs-cml-vs-cll.png USMLE Step 1 | Leukemia: AML vs ALL vs CML vs CLL, Myeloid vs Lymphoid, Acute vs Chronic https://medservatory.com/thumbs/aml-vs-all-vs-cml-vs-cll.png AML vs ALL vs CML vs CLL: sort leukemias by lineage, maturity and age, and match each to its hallmark: Auer rods, TdT, Philadelphia chromosome, smudge cells. https://www.youtube-nocookie.com/embed/SwpPfznMUt0 344 2026-11-15T09:10:00+00:00 2026-11-15T09:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/haematology-oncology/oncogenes-vs-tumour-suppressor-genes-two-hit https://medservatory.com/thumbs/oncogenes-vs-tumour-suppressor-genes-two-hit.png USMLE Step 1 | Oncogenes vs Tumour Suppressor Genes: Knudson Two-Hit Explained https://medservatory.com/thumbs/oncogenes-vs-tumour-suppressor-genes-two-hit.png Oncogenes vs tumour suppressor genes: gain of function with one hit versus loss of function with two, plus Knudson's two-hit hypothesis and a practice question. https://www.youtube-nocookie.com/embed/8ji1vF7f4A0 317 2026-11-15T09:15:00+00:00 2026-11-15T09:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg/heart-sounds-s1-s4-s2-splitting https://medservatory.com/thumbs/heart-sounds-s1-s4-s2-splitting.png USMLE Step 1 | Heart Sounds S1 to S4 and S2 Splitting Explained https://medservatory.com/thumbs/heart-sounds-s1-s4-s2-splitting.png S2 splitting explained: physiological, wide, fixed and paradoxical patterns, plus how heart sounds S1 to S4 link to the valves. USMLE Step 1 cardiology. https://www.youtube-nocookie.com/embed/AvCz4wNA0EE 326 2026-11-11T12:30:00+00:00 2026-11-11T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg/heart-murmurs-dynamic-manoeuvres https://medservatory.com/thumbs/heart-murmurs-dynamic-manoeuvres.png USMLE Step 1 | Heart Murmurs and Dynamic Manoeuvres: Valsalva, Squatting, Handgrip https://medservatory.com/thumbs/heart-murmurs-dynamic-manoeuvres.png Heart murmurs and dynamic manoeuvres: how Valsalva, squatting, handgrip and inspiration alter a murmur via preload and afterload; the HOCM exception. https://www.youtube-nocookie.com/embed/usNp0V_a7UY 315 2026-11-11T18:30:00+00:00 2026-11-11T18:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg/hocm-vs-aortic-stenosis-murmur https://medservatory.com/thumbs/hocm-vs-aortic-stenosis-murmur.png USMLE Step 1 | HOCM vs Aortic Stenosis Murmur: Valsalva, Squatting and Standing Explained https://medservatory.com/thumbs/hocm-vs-aortic-stenosis-murmur.png HOCM vs aortic stenosis murmur: how Valsalva, standing and squatting change each one, plus handgrip in HOCM, and what the carotid pulse, S4 and radiation add. https://www.youtube-nocookie.com/embed/wtCRKy6Cq4E 331 2026-11-12T00:30:00+00:00 2026-11-12T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg/ventricular-action-potential https://medservatory.com/thumbs/ventricular-action-potential.png USMLE Step 1 | Ventricular Action Potential Phases 0-4: Ion Currents and Antiarrhythmic Targets https://medservatory.com/thumbs/ventricular-action-potential.png Ventricular action potential phases 0–4 explained: the ion current behind each phase, the refractory period, and which antiarrhythmic class targets which phase. https://www.youtube-nocookie.com/embed/Omx8mmC50jo 315 2026-11-12T06:30:00+00:00 2026-11-12T06:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg/sa-node-pacemaker-potential https://medservatory.com/thumbs/sa-node-pacemaker-potential.png USMLE Step 1 | SA Node Pacemaker Potential: Funny Current and Autonomic Control of Heart Rate https://medservatory.com/thumbs/sa-node-pacemaker-potential.png SA node pacemaker potential explained: phase 4 drift, the funny current, T- and L-type calcium, and how vagal and sympathetic input change heart rate. https://www.youtube-nocookie.com/embed/IfFpK_UiqSs 317 2026-11-12T12:30:00+00:00 2026-11-12T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/heart-sounds-murmurs-ecg/ecg-waves-intervals https://medservatory.com/thumbs/ecg-waves-intervals.png USMLE Step 1 | ECG Waves and Intervals Explained: P, PR, QRS, ST, QT https://medservatory.com/thumbs/ecg-waves-intervals.png ECG waves and intervals explained: what P, PR, QRS, ST, T and QT each represent, and how a long PR or a wide QRS places a conduction delay. USMLE Step 1. https://www.youtube-nocookie.com/embed/uKce0pOOclU 329 2026-11-12T18:30:00+00:00 2026-11-12T18:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/mhc-class-1-vs-class-2-antigen-presentation https://medservatory.com/thumbs/mhc-class-1-vs-class-2-antigen-presentation.png USMLE Step 1 | MHC I vs MHC II Antigen Presentation Explained: TAP, Invariant Chain, CD8 and CD4 https://medservatory.com/thumbs/mhc-class-1-vs-class-2-antigen-presentation.png MHC I vs MHC II antigen presentation explained: the proteasome and TAP route of class I, the invariant chain and CLIP route of class II, and CD8 vs CD4 T cells. https://www.youtube-nocookie.com/embed/o0Kz4o_NWAg 303 2026-11-15T04:30:00+00:00 2026-11-15T04:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/t-cell-activation-costimulation-cd28-b7-anergy https://medservatory.com/thumbs/t-cell-activation-costimulation-cd28-b7-anergy.png USMLE Step 1 | T-Cell Activation Explained: Two Signals, CD28-B7 Costimulation and Anergy https://medservatory.com/thumbs/t-cell-activation-costimulation-cd28-b7-anergy.png T-cell activation needs two signals: TCR with peptide on MHC, then CD28 binding B7. Learn why signal one alone causes anergy and how CTLA-4 acts as a brake. https://www.youtube-nocookie.com/embed/tH7Niw4gQ3k 298 2026-11-15T04:35:00+00:00 2026-11-15T04:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/th1-th2-th17-treg-helper-t-cell-subsets https://medservatory.com/thumbs/th1-th2-th17-treg-helper-t-cell-subsets.png USMLE Step 1 | Th1, Th2, Th17 and Treg Explained: Helper T-Cell Subsets, Cytokines and Diseases https://medservatory.com/thumbs/th1-th2-th17-treg-helper-t-cell-subsets.png Th1, Th2, Th17 and Treg explained: match each helper T-cell subset to its inducing cytokines, master transcription factor, products and targets. USMLE Step 1. https://www.youtube-nocookie.com/embed/uBhte9tG8kU 313 2026-11-15T04:40:00+00:00 2026-11-15T04:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/antibody-isotypes-class-switching-igm-igg-iga-ige https://medservatory.com/thumbs/antibody-isotypes-class-switching-igm-igg-iga-ige.png USMLE Step 1 | Antibody Isotypes and Class Switching: IgM, IgG, IgA, IgE, IgD, CD40L and AID https://medservatory.com/thumbs/antibody-isotypes-class-switching-igm-igg-iga-ige.png Antibody isotypes and class switching: what IgM, IgD, IgG, IgA and IgE each do, and how CD40 ligand, cytokines and AID switch the class but keep specificity. https://www.youtube-nocookie.com/embed/Hp8NpwGnlvY 313 2026-11-15T04:45:00+00:00 2026-11-15T04:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/central-vs-peripheral-tolerance-thymic-selection-aire-tregs-fas https://medservatory.com/thumbs/central-vs-peripheral-tolerance-thymic-selection-aire-tregs-fas.png USMLE Step 1 | Central vs Peripheral Tolerance Explained: Thymic Selection, AIRE, Tregs and FAS https://medservatory.com/thumbs/central-vs-peripheral-tolerance-thymic-selection-aire-tregs-fas.png Central vs peripheral tolerance: thymic selection and AIRE, then anergy, regulatory T cells and Fas, and the disease behind each failure (APECED, IPEX, ALPS). https://www.youtube-nocookie.com/embed/4PxVosS310M 326 2026-11-15T04:50:00+00:00 2026-11-15T04:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/complement-pathways-classical-lectin-alternative https://medservatory.com/thumbs/complement-pathways-classical-lectin-alternative.png USMLE Step 1 | Complement System Explained: Classical, Lectin and Alternative Pathways, C5a, MAC https://medservatory.com/thumbs/complement-pathways-classical-lectin-alternative.png Complement system explained: how the classical, lectin and alternative pathways start, converge on C3, then opsonise, inflame and lyse through the MAC. https://www.youtube-nocookie.com/embed/W0s8_8uYzhg 324 2026-11-15T04:55:00+00:00 2026-11-15T04:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/complement-deficiencies-c1q-c3-c5-c9-c1-inhibitor https://medservatory.com/thumbs/complement-deficiencies-c1q-c3-c5-c9-c1-inhibitor.png USMLE Step 1 | Complement Deficiencies: C1q, C3, C5-C9 and C1 Inhibitor (Hereditary Angioedema) https://medservatory.com/thumbs/complement-deficiencies-c1q-c3-c5-c9-c1-inhibitor.png Complement deficiencies for USMLE Step 1: what follows when C1q, C3, C5–C9 or C1 inhibitor is missing, from lupus-like disease to Neisseria and angioedema. https://www.youtube-nocookie.com/embed/Kpg0mvWp1ds 315 2026-11-15T05:00:00+00:00 2026-11-15T05:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/hypersensitivity-types-i-to-iv https://medservatory.com/thumbs/hypersensitivity-types-i-to-iv.png USMLE Step 1 | Hypersensitivity Types I to IV: IgE, Antibody, Immune Complex, T Cell https://medservatory.com/thumbs/hypersensitivity-types-i-to-iv.png Hypersensitivity types I to IV by effector and timing: IgE, antibody on cells, immune complexes and T cells, with classic examples and the ACID memory aid. https://www.youtube-nocookie.com/embed/eDDdV1l0H2A 320 2026-11-15T05:05:00+00:00 2026-11-15T05:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/b-cell-vs-t-cell-immunodeficiency-xla-scid https://medservatory.com/thumbs/b-cell-vs-t-cell-immunodeficiency-xla-scid.png USMLE Step 1 | B-Cell vs T-Cell Immunodeficiency Explained: Infection Patterns, XLA and SCID https://medservatory.com/thumbs/b-cell-vs-t-cell-immunodeficiency-xla-scid.png B-cell vs T-cell immunodeficiency: predict the infection pattern from the arm of immunity lost, covering X-linked agammaglobulinaemia, T-cell loss and SCID. https://www.youtube-nocookie.com/embed/FrEw_iMg3uE 324 2026-11-15T05:10:00+00:00 2026-11-15T05:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/hyper-igm-syndrome-cd40-ligand-class-switching https://medservatory.com/thumbs/hyper-igm-syndrome-cd40-ligand-class-switching.png USMLE Step 1 | Hyper-IgM Syndrome Explained: CD40 Ligand, Class Switching and Infections https://medservatory.com/thumbs/hyper-igm-syndrome-cd40-ligand-class-switching.png Hyper IgM syndrome explained: how a failed CD40 ligand signal blocks class switching, the IgM, IgG, IgA and IgE profile, the infections, and AID deficiency. https://www.youtube-nocookie.com/embed/Sv3TL-VEJ6g 319 2026-11-15T05:15:00+00:00 2026-11-15T05:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/chronic-granulomatous-disease-nadph-oxidase https://medservatory.com/thumbs/chronic-granulomatous-disease-nadph-oxidase.png USMLE Step 1 | Chronic Granulomatous Disease Explained: NADPH Oxidase and the Respiratory Burst https://medservatory.com/thumbs/chronic-granulomatous-disease-nadph-oxidase.png Chronic granulomatous disease explained: how a missing NADPH oxidase breaks the respiratory burst, and why catalase-positive organisms cause the infections. https://www.youtube-nocookie.com/embed/NoUJtxotINI 320 2026-11-15T05:20:00+00:00 2026-11-15T05:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/leukocyte-adhesion-deficiency-cd18-integrins-selectins https://medservatory.com/thumbs/leukocyte-adhesion-deficiency-cd18-integrins-selectins.png USMLE Step 1 | Leukocyte Adhesion Deficiency Explained: CD18, Integrins and Extravasation https://medservatory.com/thumbs/leukocyte-adhesion-deficiency-cd18-integrins-selectins.png Leukocyte adhesion deficiency explained: follow a neutrophil through roll, activate, stick and cross, and see why CD18 loss means a high white count and no pus. https://www.youtube-nocookie.com/embed/xzc5G7zntR4 301 2026-11-15T05:25:00+00:00 2026-11-15T05:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/transplant-rejection-hyperacute-acute-chronic-gvhd https://medservatory.com/thumbs/transplant-rejection-hyperacute-acute-chronic-gvhd.png USMLE Step 1 | Transplant Rejection Explained: Hyperacute, Acute, Chronic and Graft-vs-Host Disease https://medservatory.com/thumbs/transplant-rejection-hyperacute-acute-chronic-gvhd.png Transplant rejection explained: tell hyperacute, acute and chronic rejection and graft-versus-host disease apart by timing, mechanism and biopsy findings. https://www.youtube-nocookie.com/embed/UKeR6nT9YYk 351 2026-11-15T05:30:00+00:00 2026-11-15T05:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/immunology/vaccine-types-live-inactivated-subunit-conjugate-mrna https://medservatory.com/thumbs/vaccine-types-live-inactivated-subunit-conjugate-mrna.png USMLE Step 1 | Vaccine Types Explained: Live-Attenuated, Inactivated, Subunit, Conjugate and mRNA https://medservatory.com/thumbs/vaccine-types-live-inactivated-subunit-conjugate-mrna.png Vaccine types explained: live-attenuated, inactivated, subunit, toxoid, conjugate and mRNA, the response each triggers, and why live vaccines are avoided. https://www.youtube-nocookie.com/embed/56qpLQN3wNc 341 2026-11-15T05:35:00+00:00 2026-11-15T05:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/gram-positive-vs-gram-negative-cell-walls https://medservatory.com/thumbs/gram-positive-vs-gram-negative-cell-walls.png USMLE Step 1 | Gram-Positive vs Gram-Negative Cell Walls Explained: Gram Stain, Vancomycin https://medservatory.com/thumbs/gram-positive-vs-gram-negative-cell-walls.png Gram-positive vs gram-negative cell walls: compare two envelopes, see why the Gram stain reads the wall, and why vancomycin cannot enter gram-negative cells. https://www.youtube-nocookie.com/embed/2c7WEx2yKeU 339 2026-11-15T09:20:00+00:00 2026-11-15T09:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/acid-fast-stain-mycobacteria https://medservatory.com/thumbs/acid-fast-stain-mycobacteria.png USMLE Step 1 | Acid-Fast Stain and the Mycobacterial Cell Wall Explained: Mycolic Acids https://medservatory.com/thumbs/acid-fast-stain-mycobacteria.png Acid-fast stain explained: how mycolic acids make mycobacteria hold carbol fuchsin and resist many antibiotics, plus where isoniazid and ethambutol act. https://www.youtube-nocookie.com/embed/8c47xfbcX_c 301 2026-11-15T09:25:00+00:00 2026-11-15T09:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/endotoxin-vs-exotoxin https://medservatory.com/thumbs/endotoxin-vs-exotoxin.png USMLE Step 1 | Endotoxin vs Exotoxin: LPS Lipid A, TLR4, A-B Toxins and Toxoids https://medservatory.com/thumbs/endotoxin-vs-exotoxin.png Endotoxin vs exotoxin explained: LPS lipid A and TLR4 signalling versus secreted A-B protein toxins, toxoids and superantigens. Includes a USMLE-style question. https://www.youtube-nocookie.com/embed/6qK6QuWI7wY 346 2026-11-15T09:30:00+00:00 2026-11-15T09:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/bacterial-toxins-that-raise-camp https://medservatory.com/thumbs/bacterial-toxins-that-raise-camp.png USMLE Step 1 | Toxins That Raise cAMP: Cholera, Pertussis, Anthrax https://medservatory.com/thumbs/bacterial-toxins-that-raise-camp.png Bacterial toxins that raise cAMP: how cholera, pertussis, heat-labile E. coli and anthrax toxins act through Gs, Gi or edema factor, and what each causes. https://www.youtube-nocookie.com/embed/yJvdpkGAmig 354 2026-11-15T09:35:00+00:00 2026-11-15T09:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/clostridial-toxins-compared https://medservatory.com/thumbs/clostridial-toxins-compared.png USMLE Step 1 | Clostridial Toxins Compared: Tetanus, Botulinum, C. perfringens and C. difficile https://medservatory.com/thumbs/clostridial-toxins-compared.png Clostridial toxins compared: tetanus and botulinum toxins both cut SNARE proteins, yet one is spastic and one flaccid. Plus alpha toxin and C. difficile toxins. https://www.youtube-nocookie.com/embed/pzYqq62QbhA 322 2026-11-15T09:40:00+00:00 2026-11-15T09:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/staphylococcus-vs-streptococcus-lab-identification https://medservatory.com/thumbs/staphylococcus-vs-streptococcus-lab-identification.png USMLE Step 1 | Staph vs Strep: Catalase, Coagulase, Haemolysis and Lab ID https://medservatory.com/thumbs/staphylococcus-vs-streptococcus-lab-identification.png Staph vs strep lab identification: use catalase, coagulase, novobiocin, haemolysis, bacitracin and optochin to name gram-positive cocci, step by step. https://www.youtube-nocookie.com/embed/BsauyqGzCJY 323 2026-11-15T09:45:00+00:00 2026-11-15T09:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/encapsulated-organisms-spleen-asplenia-conjugate-vaccines https://medservatory.com/thumbs/encapsulated-organisms-spleen-asplenia-conjugate-vaccines.png USMLE Step 1 | Encapsulated Organisms and the Spleen: Asplenia, OPSI and Conjugate Vaccines https://medservatory.com/thumbs/encapsulated-organisms-spleen-asplenia-conjugate-vaccines.png Encapsulated organisms and the spleen: why asplenia causes overwhelming sepsis, why polysaccharides are T-independent, and how conjugate vaccines add T help. https://www.youtube-nocookie.com/embed/JRk9HCZpvwE 308 2026-11-15T09:50:00+00:00 2026-11-15T09:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/bacterial-genetics-transformation-transduction-conjugation https://medservatory.com/thumbs/bacterial-genetics-transformation-transduction-conjugation.png USMLE Step 1 | Bacterial Genetics: Transformation, Transduction, Conjugation and Transposition https://medservatory.com/thumbs/bacterial-genetics-transformation-transduction-conjugation.png Bacterial genetics for USMLE Step 1: tell transformation, transduction, conjugation and transposition apart with one clue each, plus Hfr cells and phage toxins. https://www.youtube-nocookie.com/embed/1C4p1x27yrk 313 2026-11-15T09:55:00+00:00 2026-11-15T09:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/beta-lactamases-and-antibiotic-resistance https://medservatory.com/thumbs/beta-lactamases-and-antibiotic-resistance.png USMLE Step 1 | Beta-Lactamase and Antibiotic Resistance: PBP2a, Porins and Inhibitors https://medservatory.com/thumbs/beta-lactamases-and-antibiotic-resistance.png Beta-lactamase and antibiotic resistance explained: destroy the drug, change the target or keep it out, and which mechanism an inhibitor like clavulanate beats. https://www.youtube-nocookie.com/embed/Uu92wQH2Xb0 313 2026-11-15T10:00:00+00:00 2026-11-15T10:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/dna-rna-virus-replication https://medservatory.com/thumbs/dna-rna-virus-replication.png USMLE Step 1 | DNA vs RNA Virus Replication: Positive-Sense, Negative-Sense, Retroviruses https://medservatory.com/thumbs/dna-rna-virus-replication.png DNA vs RNA virus replication explained: where each virus replicates, what positive-sense and negative-sense mean, and which enzyme each virion must carry. https://www.youtube-nocookie.com/embed/FRppZTzo3yQ 348 2026-11-15T10:05:00+00:00 2026-11-15T10:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/hiv-life-cycle-and-drug-targets https://medservatory.com/thumbs/hiv-life-cycle-and-drug-targets.png USMLE Step 1 | HIV Life Cycle and Drug Targets: Entry, RT, Integrase, Protease https://medservatory.com/thumbs/hiv-life-cycle-and-drug-targets.png HIV life cycle and drug targets: attach, fuse, copy, insert, build, cut. Match each drug class to its step and see why treatment is lifelong. https://www.youtube-nocookie.com/embed/QWhotwfjy9Q 339 2026-11-15T10:10:00+00:00 2026-11-15T10:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/hepatitis-b-serology https://medservatory.com/thumbs/hepatitis-b-serology.png USMLE Step 1 | Hepatitis B Serology: HBsAg, Anti-HBs, Anti-HBc IgM vs IgG, Window Period https://medservatory.com/thumbs/hepatitis-b-serology.png Hepatitis B serology explained: what HBsAg, anti-HBs, HBeAg and IgM versus IgG anti-HBc mean, and how to tell acute, chronic, recovered and vaccinated apart. https://www.youtube-nocookie.com/embed/TaRlTFq9KVw 317 2026-11-15T10:15:00+00:00 2026-11-15T10:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/antifungal-mechanisms https://medservatory.com/thumbs/antifungal-mechanisms.png USMLE Step 1 | Antifungal Drugs Explained: Polyenes, Azoles, Echinocandins, Terbinafine, Flucytosine https://medservatory.com/thumbs/antifungal-mechanisms.png Antifungal drugs by target: polyenes bind ergosterol, azoles block demethylase, terbinafine blocks squalene epoxidase, echinocandins hit the wall. USMLE Step 1. https://www.youtube-nocookie.com/embed/Q-XopFIPXYM 326 2026-11-15T10:20:00+00:00 2026-11-15T10:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/microbiology/bacterial-meningitis-organisms-by-age https://medservatory.com/thumbs/bacterial-meningitis-organisms-by-age.png USMLE Step 1 | Bacterial Meningitis Organisms by Age: Newborns to Adults, Listeria and CSF https://medservatory.com/thumbs/bacterial-meningitis-organisms-by-age.png Bacterial meningitis organisms by age: newborn, child, adult and over 50 causes, how each looks on Gram stain, and how to read the bacterial CSF pattern. https://www.youtube-nocookie.com/embed/Yk2onLSRXe4 319 2026-11-15T10:25:00+00:00 2026-11-15T10:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/upper-vs-lower-motor-neuron-signs https://medservatory.com/thumbs/upper-vs-lower-motor-neuron-signs.png USMLE Step 1 | Upper vs Lower Motor Neuron Signs: Localise the Lesion https://medservatory.com/thumbs/upper-vs-lower-motor-neuron-signs.png Upper vs lower motor neuron lesions: compare tone, reflexes, the Babinski sign, fasciculations and wasting, and learn which side the signs appear on. https://www.youtube-nocookie.com/embed/VkV11pi6J84 308 2026-11-15T03:10:00+00:00 2026-11-15T03:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/ascending-sensory-pathways-dorsal-column-vs-spinothalamic https://medservatory.com/thumbs/ascending-sensory-pathways-dorsal-column-vs-spinothalamic.png USMLE Step 1 | Dorsal Column vs Spinothalamic Tract: Where Each Pathway Crosses https://medservatory.com/thumbs/ascending-sensory-pathways-dorsal-column-vs-spinothalamic.png Dorsal column vs spinothalamic tract: trace both sensory pathways, see where each crosses the midline and predict sensory loss from a cord or brainstem lesion. https://www.youtube-nocookie.com/embed/5vPRbszaTN0 301 2026-11-15T03:15:00+00:00 2026-11-15T03:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/spinal-cord-syndromes-compared https://medservatory.com/thumbs/spinal-cord-syndromes-compared.png USMLE Step 1 | Spinal Cord Syndromes Compared: Brown-Sequard, Central, Anterior and Posterior Cord https://medservatory.com/thumbs/spinal-cord-syndromes-compared.png Spinal cord syndromes compared: rebuild complete transection, Brown-Séquard, central cord, anterior cord and posterior column patterns from three tracts. https://www.youtube-nocookie.com/embed/mpW2XP-7WXQ 306 2026-11-15T03:20:00+00:00 2026-11-15T03:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/cranial-nerve-nuclei-brainstem-map https://medservatory.com/thumbs/cranial-nerve-nuclei-brainstem-map.png USMLE Step 1 | Cranial Nerve Nuclei: A Brainstem Map by Level and Position https://medservatory.com/thumbs/cranial-nerve-nuclei-brainstem-map.png Cranial nerve nuclei made simple: place each one by brainstem level (2 midbrain, 4 pons, 4 medulla) and by distance from the midline, then localise a lesion. https://www.youtube-nocookie.com/embed/oXWcmaAj25E 310 2026-11-15T03:25:00+00:00 2026-11-15T03:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/brainstem-crossed-findings-the-localisation-rule https://medservatory.com/thumbs/brainstem-crossed-findings-the-localisation-rule.png USMLE Step 1 | Brainstem Crossed Findings Explained: The Localisation Rule https://medservatory.com/thumbs/brainstem-crossed-findings-the-localisation-rule.png Brainstem crossed findings explained: why a cranial nerve sign on one side with weakness on the other localises the lesion, and how the nerve names the level. https://www.youtube-nocookie.com/embed/Cfy_Z2umR4g 290 2026-11-15T03:30:00+00:00 2026-11-15T03:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/medial-vs-lateral-medullary-syndrome https://medservatory.com/thumbs/medial-vs-lateral-medullary-syndrome.png USMLE Step 1 | Medial vs Lateral Medullary Syndrome Explained: Wallenberg, Arteries and Signs https://medservatory.com/thumbs/medial-vs-lateral-medullary-syndrome.png Medial vs lateral medullary syndrome explained: tell Wallenberg and Dejerine syndromes apart by artery, damaged structures and signs. USMLE Step 1 neuroanatomy. https://www.youtube-nocookie.com/embed/YYMBEy5wLFE 330 2026-11-15T03:35:00+00:00 2026-11-15T03:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/facial-nerve-palsy-upper-vs-lower-motor-neuron https://medservatory.com/thumbs/facial-nerve-palsy-upper-vs-lower-motor-neuron.png USMLE Step 1 | Facial Nerve Palsy: UMN vs LMN and Forehead Sparing https://medservatory.com/thumbs/facial-nerve-palsy-upper-vs-lower-motor-neuron.png Facial nerve palsy: why an upper motor neuron lesion spares the forehead and a lower motor neuron lesion does not, and how taste and tears place it. https://www.youtube-nocookie.com/embed/9nUV5OGOrEY 299 2026-11-15T03:40:00+00:00 2026-11-15T03:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/stroke-syndromes-by-artery-aca-mca-and-pca https://medservatory.com/thumbs/stroke-syndromes-by-artery-aca-mca-and-pca.png USMLE Step 1 | Stroke Syndromes by Artery: ACA, MCA and PCA Explained https://medservatory.com/thumbs/stroke-syndromes-by-artery-aca-mca-and-pca.png Stroke syndromes by artery: predict ACA, MCA and PCA deficits from the cortex each supplies and the body map inside it, with worked cases and a question. https://www.youtube-nocookie.com/embed/Ev5eq4v0BAA 281 2026-11-15T03:45:00+00:00 2026-11-15T03:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/lacunar-syndromes https://medservatory.com/thumbs/lacunar-syndromes.png USMLE Step 1 | Lacunar Stroke Syndromes Explained: Pure Motor, Pure Sensory, Ataxic Hemiparesis https://medservatory.com/thumbs/lacunar-syndromes.png Lacunar stroke syndromes explained: why a tiny deep infarct causes a dense deficit, the five classic patterns and the site of each in capsule, thalamus or pons. https://www.youtube-nocookie.com/embed/bzqFIt558KU 294 2026-11-15T03:50:00+00:00 2026-11-15T03:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/visual-pathway-lesions-field-defects https://medservatory.com/thumbs/visual-pathway-lesions-field-defects.png USMLE Step 1 | Visual Pathway Lesions and Field Defects: Bitemporal Hemianopia, Pie in the Sky https://medservatory.com/thumbs/visual-pathway-lesions-field-defects.png Visual pathway lesions and field defects: one eye before the chiasm, bitemporal at the chiasm, homonymous after it. Learn pie in the sky and pie in the floor. https://www.youtube-nocookie.com/embed/MCo5xZrIT5E 282 2026-11-15T03:55:00+00:00 2026-11-15T03:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/basal-ganglia-direct-and-indirect-pathways https://medservatory.com/thumbs/basal-ganglia-direct-and-indirect-pathways.png USMLE Step 1 | Basal Ganglia Direct and Indirect Pathways: D1, D2, Parkinson and Huntington https://medservatory.com/thumbs/basal-ganglia-direct-and-indirect-pathways.png Basal ganglia direct and indirect pathways: D1 go, D2 stop, how dopamine tips the balance, and why Parkinson has too much brake and Huntington too little. https://www.youtube-nocookie.com/embed/BKhO_6G60yM 319 2026-11-15T04:00:00+00:00 2026-11-15T04:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/cerebellar-lesion-localisation https://medservatory.com/thumbs/cerebellar-lesion-localisation.png USMLE Step 1 | Cerebellar Lesions Explained: Vermis vs Hemisphere, Truncal vs Limb Ataxia https://medservatory.com/thumbs/cerebellar-lesion-localisation.png Cerebellar lesion localisation made simple: a vermis lesion gives truncal and gait ataxia, a hemisphere lesion gives limb ataxia on the same side as the lesion. https://www.youtube-nocookie.com/embed/XCfIklXd6jQ 282 2026-11-15T04:05:00+00:00 2026-11-15T04:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/brain-herniation-syndromes https://medservatory.com/thumbs/brain-herniation-syndromes.png USMLE Step 1 | Brain Herniation Syndromes Explained: Subfalcine, Uncal, Central and Tonsillar https://medservatory.com/thumbs/brain-herniation-syndromes.png Brain herniation syndromes explained: tell subfalcine, uncal, central and tonsillar herniation apart by what is squeezed and the signs, plus Kernohan notch. https://www.youtube-nocookie.com/embed/e_Ol4P2DlLs 296 2026-11-15T04:10:00+00:00 2026-11-15T04:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/csf-flow-and-hydrocephalus https://medservatory.com/thumbs/csf-flow-and-hydrocephalus.png USMLE Step 1 | CSF Flow and Hydrocephalus: Communicating vs Obstructive vs NPH https://medservatory.com/thumbs/csf-flow-and-hydrocephalus.png CSF flow and hydrocephalus: trace CSF from the choroid plexus to the arachnoid granulations, then tell communicating, obstructive and normal pressure apart. https://www.youtube-nocookie.com/embed/fAiC2pSWpik 312 2026-11-15T04:15:00+00:00 2026-11-15T04:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/internal-capsule-corticospinal-tract https://medservatory.com/thumbs/internal-capsule-corticospinal-tract.png USMLE Step 1 | Corticospinal Tract and Internal Capsule Explained: Lesion Localisation https://medservatory.com/thumbs/internal-capsule-corticospinal-tract.png Corticospinal tract explained: trace the pathway from cortex through the internal capsule and decussation to the cord, and predict the deficit by lesion level. https://www.youtube-nocookie.com/embed/fQIA87t_nqQ 299 2026-11-15T04:20:00+00:00 2026-11-15T04:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/neuroanatomy-localisation/hypothalamic-nuclei-and-functions https://medservatory.com/thumbs/hypothalamic-nuclei-and-functions.png USMLE Step 1 | Hypothalamic Nuclei and Their Functions: ADH, Hunger, Temperature, Body Clock https://medservatory.com/thumbs/hypothalamic-nuclei-and-functions.png Hypothalamic nuclei and their functions: match supraoptic, lateral, ventromedial, anterior, posterior and suprachiasmatic nuclei to water, food, heat, sleep https://www.youtube-nocookie.com/embed/CauHapOtUVc 324 2026-11-15T04:25:00+00:00 2026-11-15T04:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/potency-vs-efficacy https://medservatory.com/thumbs/potency-vs-efficacy.png USMLE Step 1 | Potency vs Efficacy: EC50, Emax, Partial & Inverse Agonists https://medservatory.com/thumbs/potency-vs-efficacy.png Potency vs efficacy explained: EC50 sets where the dose-response curve sits, Emax sets how high it reaches. Plus full, partial and inverse agonists. https://www.youtube-nocookie.com/embed/Rpj0tddwLAs 317 2026-11-15T05:40:00+00:00 2026-11-15T05:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/competitive-vs-noncompetitive-antagonists https://medservatory.com/thumbs/competitive-vs-noncompetitive-antagonists.png USMLE Step 1 | Competitive vs Noncompetitive Antagonists Explained: Effect on EC50 and Emax https://medservatory.com/thumbs/competitive-vs-noncompetitive-antagonists.png Competitive vs noncompetitive antagonists: how each moves the dose-response curve. A competitive one raises the EC50; a noncompetitive one lowers the Emax. https://www.youtube-nocookie.com/embed/iVjvdycIsjQ 301 2026-11-15T05:45:00+00:00 2026-11-15T05:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/therapeutic-index-therapeutic-window https://medservatory.com/thumbs/therapeutic-index-therapeutic-window.png USMLE Step 1 | Therapeutic Index Explained: TD50 / ED50, Therapeutic Window and Narrow-Index Drugs https://medservatory.com/thumbs/therapeutic-index-therapeutic-window.png Therapeutic index explained: TD50 / ED50, the therapeutic window and why narrow-index drugs like warfarin and lithium need monitoring. USMLE Step 1. https://www.youtube-nocookie.com/embed/MVY4013Oa3E 301 2026-11-15T05:50:00+00:00 2026-11-15T05:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/first-pass-metabolism-bioavailability-auc https://medservatory.com/thumbs/first-pass-metabolism-bioavailability-auc.png USMLE Step 1 | First-Pass Metabolism and Bioavailability Explained: Calculating Oral F from AUC https://medservatory.com/thumbs/first-pass-metabolism-bioavailability-auc.png First-pass metabolism and bioavailability explained: the hepatic extraction ratio, routes that bypass the liver, and how to calculate oral F from AUC and dose. https://www.youtube-nocookie.com/embed/1OpotJQpuj0 318 2026-11-15T05:55:00+00:00 2026-11-15T05:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/volume-of-distribution-vd-dose-concentration https://medservatory.com/thumbs/volume-of-distribution-vd-dose-concentration.png USMLE Step 1 | Volume of Distribution Explained: Vd = Dose / Concentration, Binding https://medservatory.com/thumbs/volume-of-distribution-vd-dose-concentration.png Volume of distribution explained: Vd = dose / plasma concentration, why it can exceed body size, and how protein and tissue binding change it. Worked examples. https://www.youtube-nocookie.com/embed/xhmGKIDIUZY 317 2026-11-15T06:00:00+00:00 2026-11-15T06:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/clearance-half-life-steady-state https://medservatory.com/thumbs/clearance-half-life-steady-state.png USMLE Step 1 | Clearance and Half-Life Explained: t1/2 = 0.693 x Vd / CL, Steady State https://medservatory.com/thumbs/clearance-half-life-steady-state.png Clearance and half-life explained: t½ = 0.693 × Vd / CL, how volume of distribution and clearance set it, and why steady state takes four to five half-lives. https://www.youtube-nocookie.com/embed/yWpZLskE4IA 301 2026-11-15T06:05:00+00:00 2026-11-15T06:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/zero-order-vs-first-order-elimination https://medservatory.com/thumbs/zero-order-vs-first-order-elimination.png USMLE Step 1 | Zero-Order vs First-Order Elimination Explained: Phenytoin, Ethanol, Aspirin https://medservatory.com/thumbs/zero-order-vs-first-order-elimination.png Zero-order vs first-order elimination: constant amount versus constant fraction, why saturated enzymes leave no fixed half-life, and why phenytoin levels jump. https://www.youtube-nocookie.com/embed/YcK_1dgA3QQ 312 2026-11-15T06:10:00+00:00 2026-11-15T06:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/loading-and-maintenance-doses https://medservatory.com/thumbs/loading-and-maintenance-doses.png USMLE Step 1 | Loading Dose and Maintenance Dose Explained: Vd, Clearance and Bioavailability https://medservatory.com/thumbs/loading-and-maintenance-doses.png Loading dose and maintenance dose: loading dose = Css × Vd / F, maintenance rate = Css × CL / F. With IV and oral worked examples and organ failure. https://www.youtube-nocookie.com/embed/VDLfQC3MbYA 302 2026-11-15T06:15:00+00:00 2026-11-15T06:15:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/cyp450-inducers-inhibitors-drug-interactions https://medservatory.com/thumbs/cyp450-inducers-inhibitors-drug-interactions.png USMLE Step 1 | CYP450 Inducers vs Inhibitors Explained: Drug Interactions and Clearance https://medservatory.com/thumbs/cyp450-inducers-inhibitors-drug-interactions.png CYP450 inducers and inhibitors: see how clearance changes another drug's level, the classic names, the timing, and why narrow-margin drugs are at risk. https://www.youtube-nocookie.com/embed/olf4g3Bd9EU 316 2026-11-15T06:20:00+00:00 2026-11-15T06:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/autonomic-receptors-alpha-beta-muscarinic-g-proteins https://medservatory.com/thumbs/autonomic-receptors-alpha-beta-muscarinic-g-proteins.png USMLE Step 1 | Autonomic Receptors: Alpha, Beta, Muscarinic and G Proteins https://medservatory.com/thumbs/autonomic-receptors-alpha-beta-muscarinic-g-proteins.png Autonomic receptors made simple: map alpha, beta and muscarinic receptors to Gq, Gs and Gi, their second messengers and tissue effects, using the QISSQIQ code. https://www.youtube-nocookie.com/embed/rBy_RTx_2pE 333 2026-11-15T06:25:00+00:00 2026-11-15T06:25:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/beta-blocker-selectivity-beta-1-isa-alpha-blockade https://medservatory.com/thumbs/beta-blocker-selectivity-beta-1-isa-alpha-blockade.png USMLE Step 1 | Beta Blocker Selectivity Explained: Beta-1 Selective, ISA and Alpha Blockade https://medservatory.com/thumbs/beta-blocker-selectivity-beta-1-isa-alpha-blockade.png Beta blocker selectivity explained: sort every beta blocker by beta-1 selectivity, ISA and alpha-1 blockade, then predict its side effects. USMLE Step 1. https://www.youtube-nocookie.com/embed/C0q86lE7QKs 324 2026-11-15T06:30:00+00:00 2026-11-15T06:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/vasopressors-compared-norepinephrine-epinephrine-phenylephrine-isoproterenol https://medservatory.com/thumbs/vasopressors-compared-norepinephrine-epinephrine-phenylephrine-isoproterenol.png USMLE Step 1 | Vasopressors Compared: Norepinephrine, Epinephrine, Phenylephrine, Isoproterenol https://medservatory.com/thumbs/vasopressors-compared-norepinephrine-epinephrine-phenylephrine-isoproterenol.png Vasopressors compared by receptor: predict mean arterial pressure and heart rate for phenylephrine, norepinephrine, isoproterenol and epinephrine. https://www.youtube-nocookie.com/embed/LW5asqjde1E 346 2026-11-15T06:35:00+00:00 2026-11-15T06:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/cholinergic-toxicity-organophosphates-atropine-pralidoxime https://medservatory.com/thumbs/cholinergic-toxicity-organophosphates-atropine-pralidoxime.png USMLE Step 1 | Organophosphate Poisoning: Muscarinic vs Nicotinic, Atropine, Pralidoxime https://medservatory.com/thumbs/cholinergic-toxicity-organophosphates-atropine-pralidoxime.png Organophosphate poisoning explained: muscarinic vs nicotinic signs, the DUMBBELS mnemonic, why atropine fixes secretions and pralidoxime fixes weakness. https://www.youtube-nocookie.com/embed/upgR7cUUvI0 336 2026-11-15T06:40:00+00:00 2026-11-15T06:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/receptor-desensitization-downregulation-upregulation https://medservatory.com/thumbs/receptor-desensitization-downregulation-upregulation.png USMLE Step 1 | Receptor Desensitization and Upregulation: Beta-Blocker Withdrawal https://medservatory.com/thumbs/receptor-desensitization-downregulation-upregulation.png Receptor desensitization explained: tachyphylaxis (GRK, beta-arrestin), downregulation, upregulation, and why stopping a beta-blocker abruptly causes rebound. https://www.youtube-nocookie.com/embed/yoXuHnXiOa8 301 2026-11-15T06:45:00+00:00 2026-11-15T06:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/cell-wall-antibiotics-beta-lactams-vancomycin https://medservatory.com/thumbs/cell-wall-antibiotics-beta-lactams-vancomycin.png USMLE Step 1 | Beta-Lactams and Vancomycin Explained: PBP vs D-Ala-D-Ala https://medservatory.com/thumbs/cell-wall-antibiotics-beta-lactams-vancomycin.png Beta-lactams and vancomycin block cell-wall synthesis. See why beta-lactams bind the PBP enzyme, vancomycin binds D-Ala-D-Ala and how MRSA and VRE resist. https://www.youtube-nocookie.com/embed/VkoM9KQMxXw 304 2026-11-15T06:50:00+00:00 2026-11-15T06:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/pharmacology-principles-autonomic/protein-synthesis-inhibitors-30s-vs-50s https://medservatory.com/thumbs/protein-synthesis-inhibitors-30s-vs-50s.png USMLE Step 1 | Protein Synthesis Inhibitors: 30S vs 50S Antibiotics and Adverse Effects https://medservatory.com/thumbs/protein-synthesis-inhibitors-30s-vs-50s.png Protein synthesis inhibitors by ribosomal subunit: sort 30S and 50S antibiotics, the step each blocks, and the adverse effect that follows. USMLE Step 1. https://www.youtube-nocookie.com/embed/Gr8biqB0ZQ4 307 2026-11-15T06:55:00+00:00 2026-11-15T06:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/abg-interpretation https://medservatory.com/thumbs/abg-interpretation.png ABG Interpretation Made Simple: pH, PaCO2 & HCO3 | USMLE Step 1 https://medservatory.com/thumbs/abg-interpretation.png ABG interpretation in 3 steps: normal pH, PaCO₂ and HCO₃⁻ ranges, the Henderson–Hasselbalch 20 : 1 ratio, the four primary disorders and compensation. https://www.youtube-nocookie.com/embed/UqbHOhXBOq0 335 2026-10-23T01:32:00+01:00 2026-10-23T00:32:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/anion-gap https://medservatory.com/thumbs/anion-gap.png Anion Gap Explained: High vs Normal Gap | USMLE Step 1 https://medservatory.com/thumbs/anion-gap.png Anion gap explained: calculate Na⁺ − (Cl⁻ + HCO₃⁻), correct it for albumin, and sort a metabolic acidosis into high gap (GOLD MARK) or normal gap. https://www.youtube-nocookie.com/embed/SyFbfThBSdo 325 2026-10-23T05:30:00+01:00 2026-10-23T04:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/winters-formula https://medservatory.com/thumbs/winters-formula.png Winters' Formula Explained: Expected PCO2 in Metabolic Acidosis | USMLE Step 1 https://medservatory.com/thumbs/winters-formula.png Winters' formula explained: expected PaCO₂ = 1.5 × HCO₃⁻ + 8 ± 2. Learn to spot appropriate compensation or a hidden respiratory disorder in metabolic acidosis. https://www.youtube-nocookie.com/embed/dvZT9ryL_U4 310 2026-10-23T11:55:00+01:00 2026-10-23T10:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/delta-ratio https://medservatory.com/thumbs/delta-ratio.png Delta Ratio Explained: Find the Hidden Acid–Base Disorder | USMLE Step 1 https://medservatory.com/thumbs/delta-ratio.png Delta ratio explained: divide the rise in the anion gap by the fall in HCO₃⁻ to find a hidden normal-gap acidosis or metabolic alkalosis. Worked USMLE cases. https://www.youtube-nocookie.com/embed/lbdS2OCuI0Y 309 2026-10-23T19:00:00+01:00 2026-10-23T18:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/new-bicarbonate-ammonium-titratable-acid https://medservatory.com/thumbs/new-bicarbonate-ammonium-titratable-acid.png How the Kidney Makes New Bicarbonate: Ammonium & Titratable Acid | USMLE Step 1 https://medservatory.com/thumbs/new-bicarbonate-ammonium-titratable-acid.png How the kidney makes new bicarbonate: why reclaiming filtered HCO₃⁻ makes none, and how titratable acid and ammonium carry acid out. USMLE Step 1 renal. https://www.youtube-nocookie.com/embed/qFwXB3PNBYo 323 2026-10-25T01:30:00+01:00 2026-10-25T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/high-anion-gap-metabolic-acidosis-causes https://medservatory.com/thumbs/high-anion-gap-metabolic-acidosis-causes.png High Anion Gap Metabolic Acidosis Causes, Sorted by Mechanism (GOLD MARK) | USMLE Step 1 https://medservatory.com/thumbs/high-anion-gap-metabolic-acidosis-causes.png High anion gap metabolic acidosis causes by anion: lactate, ketoanions, toxic alcohol acids, uraemic anions and aspirin's organic acids; GOLD MARK re-sorted. https://www.youtube-nocookie.com/embed/nuVKvwcRDFo 354 2026-10-25T05:30:00+00:00 2026-10-25T05:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/osmolar-gap-toxic-alcohols https://medservatory.com/thumbs/osmolar-gap-toxic-alcohols.png Osmolar Gap Explained: Toxic Alcohols | USMLE Step 1 https://medservatory.com/thumbs/osmolar-gap-toxic-alcohols.png Osmolar gap explained: measured minus calculated osmolality, normally under 10. See why methanol and ethylene glycol open it early and the anion gap later. https://www.youtube-nocookie.com/embed/2h573OCzxzA 331 2026-10-25T09:30:00+00:00 2026-10-25T09:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/urine-anion-gap https://medservatory.com/thumbs/urine-anion-gap.png Urine Anion Gap Explained: Diarrhea vs RTA | USMLE Step 1 https://medservatory.com/thumbs/urine-anion-gap.png Urine anion gap explained: (Na⁺ + K⁺) − Cl⁻ estimates urine ammonium, so a negative gap points to diarrhea and a positive gap to distal RTA. Worked USMLE cases. https://www.youtube-nocookie.com/embed/0NBUHpZUs6E 333 2026-10-25T13:30:00+00:00 2026-10-25T13:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/renal-tubular-acidosis-types-1-2-4 https://medservatory.com/thumbs/renal-tubular-acidosis-types-1-2-4.png Renal Tubular Acidosis Types 1, 2 and 4 Explained | USMLE Step 1 https://medservatory.com/thumbs/renal-tubular-acidosis-types-1-2-4.png Renal tubular acidosis types 1, 2 and 4 compared: the broken tubule mechanism, urine pH and serum potassium that separate distal, proximal and hyperkalemic RTA. https://www.youtube-nocookie.com/embed/QphVaSzeUq4 324 2026-10-26T19:30:00+00:00 2026-10-26T19:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/metabolic-alkalosis-generation-maintenance https://medservatory.com/thumbs/metabolic-alkalosis-generation-maintenance.png Metabolic Alkalosis Explained: Generation vs Maintenance, Urine Chloride | USMLE Step 1 https://medservatory.com/thumbs/metabolic-alkalosis-generation-maintenance.png Metabolic alkalosis needs a generating event and a renal maintenance factor. Learn how urine chloride (about 20 mEq/L) splits responsive from resistant causes. https://www.youtube-nocookie.com/embed/gYNuG4Di0JA 330 2026-10-26T23:30:00+00:00 2026-10-26T23:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/vomiting-metabolic-alkalosis-paradoxical-aciduria https://medservatory.com/thumbs/vomiting-metabolic-alkalosis-paradoxical-aciduria.png Vomiting and Metabolic Alkalosis: Paradoxical Aciduria | USMLE Step 1 https://medservatory.com/thumbs/vomiting-metabolic-alkalosis-paradoxical-aciduria.png Vomiting metabolic alkalosis explained: how HCl loss, volume depletion and aldosterone cause hypochloraemic, hypokalaemic alkalosis with paradoxical aciduria. https://www.youtube-nocookie.com/embed/vS9UGdViPzo 336 2026-10-27T03:30:00+00:00 2026-10-27T03:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/bartter-vs-gitelman https://medservatory.com/thumbs/bartter-vs-gitelman.png Bartter vs Gitelman Syndrome: Loop and Thiazide Diuretics, Metabolic Alkalosis | USMLE Step 1 https://medservatory.com/thumbs/bartter-vs-gitelman.png Bartter vs Gitelman: Bartter behaves like a loop diuretic (NKCC2), Gitelman like a thiazide (NCC). Both cause alkalosis; urine calcium separates them. https://www.youtube-nocookie.com/embed/f8crjNmYxHY 321 2026-10-28T02:10:00+00:00 2026-10-28T02:10:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/respiratory-acidosis-compensation https://medservatory.com/thumbs/respiratory-acidosis-compensation.png Respiratory Acidosis: Acute vs Chronic Compensation (Expected HCO3-) | USMLE Step 1 https://medservatory.com/thumbs/respiratory-acidosis-compensation.png Respiratory acidosis compensation: HCO₃⁻ rises about 1 per 10 mm Hg of PaCO₂ when acute and about 4 when chronic. Learn the rule and why the kidney needs days. https://www.youtube-nocookie.com/embed/jqyKIUeLkt4 322 2026-10-28T09:05:00+00:00 2026-10-28T09:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/respiratory-alkalosis-compensation https://medservatory.com/thumbs/respiratory-alkalosis-compensation.png Respiratory Alkalosis Compensation: Acute vs Chronic HCO3 | USMLE Step 1 https://medservatory.com/thumbs/respiratory-alkalosis-compensation.png Respiratory alkalosis compensation: HCO₃⁻ falls about 2 per 10 mm Hg fall in PaCO₂ when acute and about 4 when chronic. Learn the recipe, limits and causes. https://www.youtube-nocookie.com/embed/vvYFKEEh8tM 333 2026-10-28T16:05:00+00:00 2026-10-28T16:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/metabolic-alkalosis-compensation-expected-pco2 https://medservatory.com/thumbs/metabolic-alkalosis-compensation-expected-pco2.png Metabolic Alkalosis Compensation Formula: Expected PaCO2 | USMLE Step 1 https://medservatory.com/thumbs/metabolic-alkalosis-compensation-expected-pco2.png Metabolic alkalosis compensation: expected PaCO₂ = 40 + 0.7 × (HCO₃⁻ − 24), with a ceiling near 55 mm Hg. Learn what a PaCO₂ above or below that means. https://www.youtube-nocookie.com/embed/gwYzeXFZjww 312 2026-10-27T07:30:00+00:00 2026-10-27T07:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/salicylate-poisoning-acid-base https://medservatory.com/thumbs/salicylate-poisoning-acid-base.png Salicylate Poisoning Acid-Base: Respiratory Alkalosis + High Anion Gap Acidosis | USMLE Step 1 https://medservatory.com/thumbs/salicylate-poisoning-acid-base.png Salicylate poisoning acid-base: early respiratory alkalosis plus high anion gap acidosis. See why pH can look normal and how Winters' formula shows it. https://www.youtube-nocookie.com/embed/bs1rwtvbPus 331 2026-10-28T23:05:00+00:00 2026-10-28T23:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/lactic-acidosis-type-a-vs-type-b https://medservatory.com/thumbs/lactic-acidosis-type-a-vs-type-b.png Type A vs Type B Lactic Acidosis Explained | USMLE Step 1 https://medservatory.com/thumbs/lactic-acidosis-type-a-vs-type-b.png Type A vs type B lactic acidosis: type A is poor perfusion, type B is faulty lactate handling with adequate perfusion. Learn the causes, thiamine and metformin. https://www.youtube-nocookie.com/embed/RxL9TqBNwck 333 2026-10-30T03:16:00+00:00 2026-10-30T03:16:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/dka-anion-gap-hyperchloremic-acidosis https://medservatory.com/thumbs/dka-anion-gap-hyperchloremic-acidosis.png DKA Anion Gap Explained: High Gap to Hyperchloraemic Acidosis | USMLE Step 1 https://medservatory.com/thumbs/dka-anion-gap-hyperchloremic-acidosis.png DKA anion gap explained: why ketoacids give a high gap, and why ketoanion loss in urine plus saline chloride can leave a normal-gap, hyperchloraemic acidosis. https://www.youtube-nocookie.com/embed/RA-3XcWx5Zk 342 2026-10-30T10:20:00+00:00 2026-10-30T10:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/acidosis-hyperkalemia-potassium-shift https://medservatory.com/thumbs/acidosis-hyperkalemia-potassium-shift.png Acidosis and Hyperkalemia Explained: Potassium Shifts and pH | USMLE Step 1 https://medservatory.com/thumbs/acidosis-hyperkalemia-potassium-shift.png Acidosis and hyperkalemia explained: how acidemia, insulin and beta-2 agonists shift potassium, and why mineral acid acidosis shifts it more than organic acid. https://www.youtube-nocookie.com/embed/zwII_nF3Yj0 343 2026-10-30T17:20:00+00:00 2026-10-30T17:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/stepwise-abg-interpretation-algorithm https://medservatory.com/thumbs/stepwise-abg-interpretation-algorithm.png ABG Interpretation in 6 Steps: Acid-Base Algorithm | USMLE Step 1 https://medservatory.com/thumbs/stepwise-abg-interpretation-algorithm.png ABG interpretation in 6 steps: pH, primary disorder, compensation, anion gap, delta ratio and context. See how one algorithm exposes a hidden second disorder. https://www.youtube-nocookie.com/embed/tgmpRnugb0I 332 2026-10-31T00:20:00+00:00 2026-10-31T00:20:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-acid-base/acid-base-practice-cases-abg-vignettes https://medservatory.com/thumbs/acid-base-practice-cases-abg-vignettes.png Acid-Base Practice Cases: 3 ABG Vignettes (Single, Mixed, Triple) | USMLE Step 1 https://medservatory.com/thumbs/acid-base-practice-cases-abg-vignettes.png Acid-base practice cases: three ABG vignettes solved with one six-step algorithm. See how Winters' formula and the delta ratio expose a second disorder. https://www.youtube-nocookie.com/embed/yHN_7xysb3I 344 2026-11-02T05:35:00+00:00 2026-11-02T05:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/gfr-starling-forces-glomerulus https://medservatory.com/thumbs/gfr-starling-forces-glomerulus.png GFR Explained: Starling Forces at the Glomerulus | USMLE Step 1 https://medservatory.com/thumbs/gfr-starling-forces-glomerulus.png GFR and Starling forces at the glomerulus: net filtration pressure is capillary pressure minus Bowman's space and oncotic pressure. Predict how GFR changes. https://www.youtube-nocookie.com/embed/OYSSvpEMQMU 325 2026-11-02T12:30:00+00:00 2026-11-02T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/afferent-vs-efferent-arteriole-gfr-rpf-filtration-fraction https://medservatory.com/thumbs/afferent-vs-efferent-arteriole-gfr-rpf-filtration-fraction.png Afferent vs Efferent Arteriole: GFR, RPF and Filtration Fraction | USMLE Step 1 https://medservatory.com/thumbs/afferent-vs-efferent-arteriole-gfr-rpf-filtration-fraction.png Afferent vs efferent arteriole: how constriction or dilation changes GFR, RPF and filtration fraction, and why NSAIDs and ACE inhibitors raise creatinine. https://www.youtube-nocookie.com/embed/9OFBRXt3v6w 316 2026-11-02T19:30:00+00:00 2026-11-02T19:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/renal-clearance-inulin-creatinine-pah https://medservatory.com/thumbs/renal-clearance-inulin-creatinine-pah.png Renal Clearance Explained: Inulin, Creatinine and PAH | USMLE Step 1 https://medservatory.com/thumbs/renal-clearance-inulin-creatinine-pah.png Renal clearance explained: C = U × V / P, why inulin clearance equals GFR, what creatinine and PAH clearance estimate, and how to read tubular handling. https://www.youtube-nocookie.com/embed/qDlJWOqb20A 320 2026-11-03T02:30:00+00:00 2026-11-03T02:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/glucose-transport-maximum-splay-sglt2 https://medservatory.com/thumbs/glucose-transport-maximum-splay-sglt2.png Glucose Transport Maximum and Splay Explained: Glucosuria and SGLT2 Inhibitors | USMLE Step 1 https://medservatory.com/thumbs/glucose-transport-maximum-splay-sglt2.png Glucose transport maximum explained: SGLT2 and SGLT1, filtered load, renal threshold, splay, excretion = load − Tm, and why SGLT2 inhibitors cause glucosuria. https://www.youtube-nocookie.com/embed/EQD4rbA5v1k 295 2026-11-06T04:00:00+00:00 2026-11-06T04:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/countercurrent-multiplier-urine-concentration https://medservatory.com/thumbs/countercurrent-multiplier-urine-concentration.png Countercurrent Multiplier Explained: How the Kidney Concentrates Urine | USMLE Step 1 https://medservatory.com/thumbs/countercurrent-multiplier-urine-concentration.png Countercurrent multiplier explained: how the loop of Henle's single effect, urea recycling and vasa recta build the medullary gradient that concentrates urine. https://www.youtube-nocookie.com/embed/WNF9gf4Gnk4 302 2026-11-06T07:00:00+00:00 2026-11-06T07:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/aldosterone-adh-distal-nephron https://medservatory.com/thumbs/aldosterone-adh-distal-nephron.png Aldosterone and ADH in the Distal Nephron Explained: ENaC, ROMK, Aquaporin-2 | USMLE Step 1 https://medservatory.com/thumbs/aldosterone-adh-distal-nephron.png Aldosterone and ADH in the distal nephron explained: ENaC, ROMK, the lumen-negative voltage, V2 receptor, aquaporin-2, and effects on Na⁺, K⁺, H⁺ and water. https://www.youtube-nocookie.com/embed/owqWmQKRjAo 320 2026-11-06T10:00:00+00:00 2026-11-06T10:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/diuretics-by-nephron-segment https://medservatory.com/thumbs/diuretics-by-nephron-segment.png Diuretics by Nephron Segment: Loop, Thiazide, Acetazolamide and K-Sparing | USMLE Step 1 https://medservatory.com/thumbs/diuretics-by-nephron-segment.png Diuretics by nephron segment: map loop, thiazide, acetazolamide and potassium-sparing drugs to their transporters and predict each drug's electrolyte pattern. https://www.youtube-nocookie.com/embed/dU_xWR1sBRs 353 2026-11-06T13:00:00+00:00 2026-11-06T13:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/renal-physiology/raas-renin-angiotensin-aldosterone https://medservatory.com/thumbs/raas-renin-angiotensin-aldosterone.png USMLE Step 1 | RAAS Explained: Renin Release, Angiotensin II and Aldosterone https://medservatory.com/thumbs/raas-renin-angiotensin-aldosterone.png RAAS explained for USMLE Step 1: what triggers renin release, how angiotensin II protects GFR, and how aldosterone keeps sodium but wastes potassium and H⁺. https://www.youtube-nocookie.com/embed/LV8sWV15lck 323 2026-11-08T06:00:00+00:00 2026-11-08T06:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/lung-volumes-capacities-spirometry https://medservatory.com/thumbs/lung-volumes-capacities-spirometry.png USMLE Step 1 | Lung Volumes and Capacities: Spirometry, RV and FRC Explained https://medservatory.com/thumbs/lung-volumes-capacities-spirometry.png Lung volumes and capacities on a spirogram: TV, IRV, ERV, RV, VC, FRC and TLC, and why spirometry cannot measure residual volume. Includes a practice question. https://www.youtube-nocookie.com/embed/lmGEfhtN9Ek 326 2026-11-13T00:30:00+00:00 2026-11-13T00:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/obstructive-vs-restrictive-lung-disease-fev1-fvc https://medservatory.com/thumbs/obstructive-vs-restrictive-lung-disease-fev1-fvc.png USMLE Step 1 | Obstructive vs Restrictive Lung Disease: FEV1/FVC, TLC and Flow-Volume Loops https://medservatory.com/thumbs/obstructive-vs-restrictive-lung-disease-fev1-fvc.png Obstructive vs restrictive lung disease: read FEV1/FVC, total lung capacity and the flow-volume loop, with the 0.70 exam cut-off and two worked patients. https://www.youtube-nocookie.com/embed/Bza22xLzp5I 323 2026-11-15T01:39:00+00:00 2026-11-15T01:39:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/compliance-surface-tension-surfactant https://medservatory.com/thumbs/compliance-surface-tension-surfactant.png USMLE Step 1 | Lung Compliance, Laplace and Surfactant Explained: Why Alveoli Do Not Collapse https://medservatory.com/thumbs/compliance-surface-tension-surfactant.png Lung compliance, the law of Laplace (P = 2T/r) and surfactant: why alveoli stay open, emphysema vs fibrosis, and neonatal RDS with the L/S ratio. https://www.youtube-nocookie.com/embed/apsn7E60Uls 323 2026-11-15T02:30:00+00:00 2026-11-15T02:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/vq-mismatch-shunt-dead-space https://medservatory.com/thumbs/vq-mismatch-shunt-dead-space.png USMLE Step 1 | V/Q Mismatch Explained: Shunt vs Dead Space and the Oxygen Test https://medservatory.com/thumbs/vq-mismatch-shunt-dead-space.png V/Q mismatch explained: shunt (V/Q 0) responds poorly to oxygen, while dead space and low V/Q respond. Learn the oxygen test that sorts them for Step 1. https://www.youtube-nocookie.com/embed/hU8Ps3a7aHw 318 2026-11-15T02:35:00+00:00 2026-11-15T02:35:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/a-a-gradient-alveolar-gas-equation https://medservatory.com/thumbs/a-a-gradient-alveolar-gas-equation.png USMLE Step 1 | A-a Gradient Explained: Alveolar Gas Equation and Causes of Hypoxemia https://medservatory.com/thumbs/a-a-gradient-alveolar-gas-equation.png A-a gradient explained: use the alveolar gas equation to calculate it, then tell hypoventilation from lung disease as the cause of hypoxaemia. Worked cases. https://www.youtube-nocookie.com/embed/H6gVU2_HChU 339 2026-11-15T02:40:00+00:00 2026-11-15T02:40:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/oxygen-hemoglobin-dissociation-curve https://medservatory.com/thumbs/oxygen-hemoglobin-dissociation-curve.png USMLE Step 1 | Oxygen-Hemoglobin Dissociation Curve: P50, Right and Left Shifts, O2 Content https://medservatory.com/thumbs/oxygen-hemoglobin-dissociation-curve.png Oxygen-hemoglobin dissociation curve explained: the sigmoid shape, P50, right and left shifts, and why saturation is not oxygen content. USMLE Step 1. https://www.youtube-nocookie.com/embed/MYe6F0Ukl6c 319 2026-11-15T02:45:00+00:00 2026-11-15T02:45:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/co2-transport-bohr-haldane-effects https://medservatory.com/thumbs/co2-transport-bohr-haldane-effects.png USMLE Step 1 | CO2 Transport Explained: Bicarbonate, Chloride Shift, Bohr vs Haldane Effect https://medservatory.com/thumbs/co2-transport-bohr-haldane-effects.png CO₂ transport explained: bicarbonate, carbamino and dissolved CO₂, the chloride shift, and how to tell the Bohr effect from the Haldane effect. USMLE Step 1. https://www.youtube-nocookie.com/embed/HiHb7Dlxqxc 329 2026-11-15T02:50:00+00:00 2026-11-15T02:50:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/chemoreceptors-oxygen-copd-hypercapnia https://medservatory.com/thumbs/chemoreceptors-oxygen-copd-hypercapnia.png USMLE Step 1 | Central vs Peripheral Chemoreceptors and Oxygen-Induced Hypercapnia (COPD) https://medservatory.com/thumbs/chemoreceptors-oxygen-copd-hypercapnia.png Central vs peripheral chemoreceptors explained: what each senses, why a CO₂ retainer can lean on low oxygen, and what causes oxygen-induced hypercapnia. https://www.youtube-nocookie.com/embed/K6fqE0NB1F8 327 2026-11-15T02:55:00+00:00 2026-11-15T02:55:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/hypoxic-pulmonary-vasoconstriction-cor-pulmonale https://medservatory.com/thumbs/hypoxic-pulmonary-vasoconstriction-cor-pulmonale.png USMLE Step 1 | Hypoxic Pulmonary Vasoconstriction, Pulmonary Hypertension and Cor Pulmonale https://medservatory.com/thumbs/hypoxic-pulmonary-vasoconstriction-cor-pulmonale.png Hypoxic pulmonary vasoconstriction explained: how it keeps V/Q matched, why chronic hypoxia in COPD causes pulmonary hypertension and cor pulmonale. Step 1. https://www.youtube-nocookie.com/embed/gse09IZhdHE 341 2026-11-15T03:00:00+00:00 2026-11-15T03:00:00.000Z monthly 0.9 https://medservatory.com/usmle-step-1/respiratory-physiology/co-cyanide-methaemoglobin-spo2-pao2 https://medservatory.com/thumbs/co-cyanide-methaemoglobin-spo2-pao2.png USMLE Step 1 | CO, Cyanide and Methaemoglobin Explained: Why SpO2 and PaO2 Fool You https://medservatory.com/thumbs/co-cyanide-methaemoglobin-spo2-pao2.png CO, cyanide and methaemoglobin explained: how each poison fools SpO₂ and PaO₂ while oxygen content or tissue use fails, and how to tell them apart for Step 1. https://www.youtube-nocookie.com/embed/jWTgA9CEWUA 334 2026-11-15T03:05:00+00:00 2026-11-15T03:05:00.000Z monthly 0.9 https://medservatory.com/usmle-step-2-ck/emergency-medicine/chest-pain-first-10-minutes https://medservatory.com/thumbs/chest-pain-first-10-minutes.png Chest Pain Approach: The First 10 Minutes | USMLE Step 2 CK https://medservatory.com/thumbs/chest-pain-first-10-minutes.png A chest pain approach for USMLE Step 2 CK: check stability, get a 12-lead ECG within 10 minutes, think through the can't-miss six, then troponin and risk. https://www.youtube-nocookie.com/embed/ycKNemN63cI 321 2026-10-24T09:30:00+01:00 2026-10-24T08:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-2-ck/emergency-medicine/high-sensitivity-troponin https://medservatory.com/thumbs/high-sensitivity-troponin.png High-Sensitivity Troponin Explained: Myocardial Injury vs MI in Suspected ACS | USMLE Step 2 CK https://medservatory.com/thumbs/high-sensitivity-troponin.png High-sensitivity troponin for USMLE Step 2 CK: serial ECGs, when to repeat hs-troponin, single-sample rule-out, and myocardial injury vs type 1 and type 2 MI. https://www.youtube-nocookie.com/embed/2UgiZzXAUxc 323 2026-10-24T13:30:00+01:00 2026-10-24T12:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-2-ck/emergency-medicine/stemi-reperfusion-decision https://medservatory.com/thumbs/stemi-reperfusion-decision.png STEMI vs NSTEMI: The Reperfusion Decision | USMLE Step 2 CK https://medservatory.com/thumbs/stemi-reperfusion-decision.png STEMI vs NSTEMI for Step 2 CK: the ECG criteria, primary PCI within 90 or 120 minutes, when to give fibrinolysis, and risk-timed angiography in NSTE-ACS. https://www.youtube-nocookie.com/embed/ye-6OrcY7Vs 318 2026-10-24T17:30:00+01:00 2026-10-24T16:30:00.000Z monthly 0.9 https://medservatory.com/usmle-step-2-ck/emergency-medicine/stemi-vs-aortic-dissection https://medservatory.com/thumbs/stemi-vs-aortic-dissection.png Chest Pain Next Best Step: STEMI or Aortic Dissection? A Case Walkthrough | USMLE Step 2 CK https://medservatory.com/thumbs/stemi-vs-aortic-dissection.png Chest pain next best step: walk a Step 2 CK case with inferior ST elevation and spot the aortic dissection clues that mean CT angiography, not PCI or lysis. https://www.youtube-nocookie.com/embed/L3kw9Ynm4y0 284 2026-10-24T21:30:00+01:00 2026-10-24T20:30:00.000Z monthly 0.9 https://medservatory.com/a-level-biology 2026-11-19T09:00:00.000Z weekly 0.8 https://medservatory.com/a-level-biology/3-1-biological-molecules 2026-11-05T18:40:00.000Z weekly 0.8 https://medservatory.com/a-level-biology/3-2-cells 2026-11-17T17:00:00.000Z weekly 0.8 https://medservatory.com/a-level-biology/3-3-exchange-with-the-environment 2026-11-19T09:00:00.000Z weekly 0.8 https://medservatory.com/a-level-biology/3-1-biological-molecules/condensation-and-hydrolysis-reactions https://medservatory.com/thumbs/alevel/condensation-and-hydrolysis-reactions.jpg Condensation and Hydrolysis Reactions | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/condensation-and-hydrolysis-reactions.jpg How monomers join into polymers by condensation (a bond forms and water is released) and how hydrolysis breaks them apart again using water. https://www.youtube-nocookie.com/embed/D728ULe_zxk 190 2026-11-04T11:00:00+00:00 2026-11-04T11:00:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/maltose-sucrose-lactose-glycosidic-bonds https://medservatory.com/thumbs/alevel/maltose-sucrose-lactose-glycosidic-bonds.jpg Maltose, Sucrose, Lactose: Glycosidic Bonds | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/maltose-sucrose-lactose-glycosidic-bonds.jpg How two monosaccharides join by condensation to form a glycosidic bond, and which pairs make the three disaccharides: maltose, sucrose and lactose. https://www.youtube-nocookie.com/embed/DygCQqGRukg 221 2026-11-04T12:15:00+00:00 2026-11-04T12:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/alpha-vs-beta-glucose-starch-vs-cellulose https://medservatory.com/thumbs/alevel/alpha-vs-beta-glucose-starch-vs-cellulose.jpg Alpha vs Beta Glucose: Starch vs Cellulose | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/alpha-vs-beta-glucose-starch-vs-cellulose.jpg Why alpha-glucose gives starch and glycogen (storage) while beta-glucose gives cellulose (structure), and how each structure fits its function. https://www.youtube-nocookie.com/embed/bf67d4KTmUU 295 2026-11-04T13:15:00+00:00 2026-11-04T13:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/benedicts-and-iodine-tests-explained https://medservatory.com/thumbs/alevel/benedicts-and-iodine-tests-explained.jpg Benedict's and Iodine Tests Explained | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/benedicts-and-iodine-tests-explained.jpg How to test for reducing sugars, non-reducing sugars and starch with Benedict's reagent and iodine, including the acid hydrolysis route for non-reducing… https://www.youtube-nocookie.com/embed/OyoGaQsuyrY 235 2026-11-04T14:15:00+00:00 2026-11-04T14:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/triglycerides-saturated-vs-unsaturated-fats https://medservatory.com/thumbs/alevel/triglycerides-saturated-vs-unsaturated-fats.jpg Triglycerides: Saturated vs Unsaturated Fats | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/triglycerides-saturated-vs-unsaturated-fats.jpg How a triglyceride forms from glycerol and three fatty acids by condensation (ester bonds), and how saturated and unsaturated fatty acids differ. https://www.youtube-nocookie.com/embed/LXqSF_NSh5Y 243 2026-11-04T15:15:00+00:00 2026-11-04T15:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/phospholipids-vs-triglycerides-emulsion-test https://medservatory.com/thumbs/alevel/phospholipids-vs-triglycerides-emulsion-test.jpg Phospholipids vs Triglycerides: Emulsion Test | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/phospholipids-vs-triglycerides-emulsion-test.jpg How the hydrophilic head and hydrophobic tails of a phospholipid make it form layers on water while triglycerides form droplets, plus the emulsion test… https://www.youtube-nocookie.com/embed/xDeSnQf-gwM 254 2026-11-04T16:15:00+00:00 2026-11-04T16:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/amino-acids-and-peptide-bonds-explained https://medservatory.com/thumbs/alevel/amino-acids-and-peptide-bonds-explained.jpg Amino Acids and Peptide Bonds Explained | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/amino-acids-and-peptide-bonds-explained.jpg The general structure of an amino acid, how the 20 amino acids differ in their R group, and how a condensation reaction forms a peptide bond in a… https://www.youtube-nocookie.com/embed/1gpGPzK0yJ0 211 2026-11-04T17:15:00+00:00 2026-11-04T17:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/protein-structure-primary-to-quaternary https://medservatory.com/thumbs/alevel/protein-structure-primary-to-quaternary.jpg Protein Structure: Primary to Quaternary | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/protein-structure-primary-to-quaternary.jpg The four levels of protein structure (primary, secondary, tertiary, quaternary), the bonds that hold each level, and how one changed amino acid can alter… https://www.youtube-nocookie.com/embed/MRKk7GjIRkM 293 2026-11-04T18:15:00+00:00 2026-11-04T18:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/globular-vs-fibrous-proteins-and-biuret-test https://medservatory.com/thumbs/alevel/globular-vs-fibrous-proteins-and-biuret-test.jpg Globular vs Fibrous Proteins and Biuret Test | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/globular-vs-fibrous-proteins-and-biuret-test.jpg How protein shape decides its job, comparing globular and fibrous proteins (collagen), and how the biuret test shows that protein is present. https://www.youtube-nocookie.com/embed/_VoY_gkyGa4 225 2026-11-04T19:15:00+00:00 2026-11-04T19:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/how-enzymes-work-active-site-and-induced-fit https://medservatory.com/thumbs/alevel/how-enzymes-work-active-site-and-induced-fit.jpg How Enzymes Work: Active Site and Induced Fit | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/how-enzymes-work-active-site-and-induced-fit.jpg How enzymes speed up reactions by lowering activation energy at the active site, why each enzyme is specific, and how the induced fit model replaced lock… https://www.youtube-nocookie.com/embed/SFNAX97BQLA 275 2026-11-04T20:15:00+00:00 2026-11-04T20:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/enzymes-temperature-and-ph-effects https://medservatory.com/thumbs/alevel/enzymes-temperature-and-ph-effects.jpg Enzymes: Temperature and pH Effects | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/enzymes-temperature-and-ph-effects.jpg How temperature and pH change the rate of an enzyme-controlled reaction, and why high temperature or extreme pH denatures the enzyme by breaking bonds in… https://www.youtube-nocookie.com/embed/5TutuUZG4Qc 276 2026-11-04T21:15:00+00:00 2026-11-04T21:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/enzyme-rate-graphs-why-the-plateau https://medservatory.com/thumbs/alevel/enzyme-rate-graphs-why-the-plateau.jpg Enzyme Rate Graphs: Why the Plateau | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/enzyme-rate-graphs-why-the-plateau.jpg Why the rate of an enzyme-controlled reaction rises with substrate concentration then levels off, and which factor is limiting at the plateau. https://www.youtube-nocookie.com/embed/fmUnTWiL6E0 229 2026-11-04T22:15:00+00:00 2026-11-04T22:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/competitive-vs-non-competitive-inhibitors https://medservatory.com/thumbs/alevel/competitive-vs-non-competitive-inhibitors.jpg Competitive vs Non-Competitive Inhibitors | A-level Biology (AQA) https://medservatory.com/thumbs/alevel/competitive-vs-non-competitive-inhibitors.jpg How competitive and non-competitive inhibitors slow an enzyme-controlled reaction, where each binds, and what raising substrate concentration does in each… https://www.youtube-nocookie.com/embed/DYMYpcWqwaA 265 2026-11-04T23:15:00+00:00 2026-11-04T23:15:00.000Z monthly 0.9 https://medservatory.com/a-level-biology/3-1-biological-molecules/required-practical-1-enzyme-rates https://medservatory.com/thumbs/alevel/required-practical-1-enzyme-rates.jpg Required Practical 1: Enzyme Rates | 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