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United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease Syllabus

The Organ Systems: Structure, Function, and Disease syllabus for United States Medical Licensing Examination (USMLE) in full: 6 chapters, 30 topics and 41 sub-topics, every one listed below, plus 51 Organ Systems: Structure, Function, and Disease flashcards with answers.

6Chapters
30Topics
41Sub-topics
51Flashcards

Organ Systems: Structure, Function, and Disease syllabus: all 6 chapters

Expand any chapter to see its topics and sub-topics.

  1. Cardiovascular System

     5 topics
    • Cardiac physiology
      • Cardiac cycle and pressure-volume loops
      • Action potentials and conduction
    • Hemodynamics and circulatory regulation
      • Cardiac output and Starling forces
      • Baroreceptor and RAAS control
    • Ischemic and valvular heart disease
      • Coronary artery disease and MI
      • Valvular lesions and murmurs
    • Heart failure and cardiomyopathies
    • Cardiovascular pharmacology
      • Antihypertensives and diuretics
      • Antiarrhythmics and antianginals

  2. Respiratory System

     5 topics
    • Pulmonary mechanics and ventilation
      • Lung volumes and compliance
      • Work of breathing
    • Gas exchange and transport
      • Oxygen-hemoglobin dissociation
      • V/Q mismatch and hypoxemia
    • Obstructive and restrictive disease
      • Asthma and COPD
      • Interstitial lung disease
    • Pulmonary vascular and infectious disease
      • Pulmonary embolism and hypertension
      • Pneumonia and tuberculosis
    • Respiratory pharmacology

  3. Renal, GI, and Endocrine Systems

     5 topics
    • Renal physiology and acid-base balance
      • Glomerular filtration and clearance
      • Electrolyte and acid-base disorders
    • Renal pathology and pharmacology
      • Nephritic and nephrotic syndromes
      • Diuretics and kidney injury
    • GI physiology and pathology
      • Motility, secretion, and absorption
      • Hepatobiliary and GI disease
    • Endocrine axes and disorders
      • Hypothalamic-pituitary regulation
      • Thyroid, adrenal, and diabetes
    • Reproductive endocrinology
      • Menstrual cycle and pregnancy
      • Sexual differentiation

  4. Nervous System and Special Senses

     5 topics
    • Neuroanatomy
      • Cerebral cortex and pathways
      • Brainstem and cranial nerves
    • Neurophysiology
      • Synaptic transmission
      • Sensory and motor systems
    • Cerebrovascular and demyelinating disease
      • Stroke syndromes
      • Multiple sclerosis
    • Neurodegenerative and seizure disorders
    • Neuropharmacology and special senses
      • Ophthalmology and audiovestibular

  5. Musculoskeletal, Skin, and Connective Tissue

     5 topics
    • Bone and joint physiology
      • Bone remodeling and calcium homeostasis
    • Muscle structure and function
      • Excitation-contraction coupling
    • Arthritides and autoimmune disease
      • Rheumatoid arthritis and SLE
      • Crystal arthropathies
    • Dermatologic pathology
    • MSK and dermatologic pharmacology

  6. Hematologic and Lymphoreticular System

     5 topics
    • Hematopoiesis and red cell physiology
    • Anemias
      • Microcytic, macrocytic, hemolytic
    • Hemostasis and coagulation disorders
      • Platelet and clotting factor defects
    • Leukemias and lymphomas
      • Acute and chronic leukemias
      • Hodgkin and non-Hodgkin lymphoma
    • Hematologic and anticoagulant pharmacology

United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease flashcards — 51 questions with answers

  1. What is the formula for cardiac output (CO), and what are its two determinants?

    CO = Stroke Volume × Heart Rate. It is determined by stroke volume (preload, afterload, contractility) and heart rate.

  2. Define ejection fraction (EF) and give the normal range.

    EF = Stroke Volume / End-Diastolic Volume. Normal is approximately 55–70%. Reduced EF (<40%) indicates systolic dysfunction.

  3. During the cardiac cycle, when are the aortic and mitral valves both closed?

    During isovolumetric contraction and isovolumetric relaxation, when ventricular volume is constant and no blood enters or leaves the ventricle.

  4. What does the Frank-Starling mechanism describe?

    Increased ventricular end-diastolic volume (preload) stretches sarcomeres, increasing force of contraction and stroke volume — the heart pumps what it receives.

  5. State Ohm's law applied to hemodynamics relating pressure, flow, and resistance.

    ΔP = Q × R, where ΔP is pressure gradient, Q is flow (cardiac output), and R is total peripheral resistance. Thus MAP ≈ CO × TPR.

  6. How is mean arterial pressure (MAP) estimated from systolic (SBP) and diastolic (DBP) pressures?

    MAP ≈ DBP + 1/3 (SBP − DBP), i.e., diastolic pressure plus one-third of the pulse pressure.

  7. By the Poiseuille equation, how does vessel radius affect resistance to flow?

    Resistance is inversely proportional to the fourth power of the radius (R ∝ 1/r⁴), so small radius changes cause large resistance changes.

  8. What baroreceptor reflex response occurs when blood pressure suddenly falls?

    Decreased carotid sinus/aortic arch stretch reduces afferent firing, causing increased sympathetic and decreased parasympathetic tone — raising HR, contractility, and vasoconstriction.

  9. What ECG finding and artery are classically associated with an inferior wall MI?

    ST elevation in leads II, III, and aVF, usually due to occlusion of the right coronary artery (RCA).

  10. Contrast the murmur of aortic stenosis with aortic regurgitation.

    Aortic stenosis: crescendo-decrescendo systolic ejection murmur radiating to carotids. Aortic regurgitation: early diastolic decrescendo blowing murmur with wide pulse pressure.

  11. What is the most common cause of mitral stenosis worldwide?

    Rheumatic heart disease, resulting from prior group A streptococcal infection causing fibrosis and fusion of the mitral valve leaflets.

  12. Distinguish systolic from diastolic heart failure by ejection fraction.

    Systolic (HFrEF): reduced EF from impaired contractility. Diastolic (HFpEF): preserved EF with impaired ventricular filling due to a stiff, non-compliant ventricle.

  13. Name the three major types of cardiomyopathy and their hallmark functional defect.

    Dilated (systolic dysfunction, dilated chambers), Hypertrophic (diastolic dysfunction, asymmetric septal hypertrophy), Restrictive (impaired filling from stiff walls).

  14. Which heart failure drug classes reduce mortality in HFrEF?

    ACE inhibitors/ARBs (or ARNI), beta-blockers (carvedilol, metoprolol succinate, bisoprolol), mineralocorticoid antagonists (spironolactone), and SGLT2 inhibitors.

  15. What is the mechanism of nitroglycerin in angina relief?

    It releases nitric oxide, increasing cGMP and causing smooth muscle relaxation — predominantly venodilation, reducing preload and myocardial oxygen demand.

  16. How does digoxin increase cardiac contractility?

    It inhibits the Na⁺/K⁺-ATPase, raising intracellular Na⁺, which reduces Na⁺/Ca²⁺ exchanger activity, increasing intracellular calcium and contractility.

  17. Define compliance of the lung and identify the elastic element opposing it.

    Compliance = ΔVolume/ΔPressure (lung distensibility). It is opposed by elastic recoil from elastin fibers and alveolar surface tension.

  18. What is the role of pulmonary surfactant, and which cells produce it?

    Surfactant lowers alveolar surface tension, preventing collapse (atelectasis) and increasing compliance. It is produced by type II pneumocytes.

  19. Define anatomic dead space and give its approximate normal value.

    The volume of conducting airways that does not participate in gas exchange — approximately 150 mL in a normal adult.

  20. Write the alveolar gas equation for PAO₂.

    PAO₂ = PIO₂ − PaCO�2/R = FiO₂(Patm − PH₂O) − PaCO₂/0.8. At sea level on room air ≈ 150 − PaCO₂/0.8.

Show the other 31 Organ Systems: Structure, Function, and Disease flashcards

  1. What factors shift the oxygen-hemoglobin dissociation curve to the right?

    Increased CO₂, increased H⁺ (low pH), increased temperature, and increased 2,3-BPG — all decrease O₂ affinity, favoring tissue unloading (Bohr effect).

  2. In what three forms is CO₂ transported in the blood?

    As bicarbonate (~70%, via carbonic anhydrase), bound to hemoglobin as carbaminohemoglobin (~23%), and dissolved in plasma (~7%).

  3. Contrast the FEV1/FVC ratio in obstructive versus restrictive lung disease.

    Obstructive: decreased FEV1/FVC (<0.7). Restrictive: normal or increased FEV1/FVC with reduced total lung capacity.

  4. What are the two phenotypes of COPD and their pathology?

    Emphysema (alveolar wall destruction, enlarged airspaces, 'pink puffer') and chronic bronchitis (productive cough ≥3 months/2 years, mucus gland hyperplasia, 'blue bloater').

  5. Define a pulmonary embolism's classic V/Q relationship.

    PE creates dead space ventilation — ventilation without perfusion (high V/Q), causing hypoxemia and an increased A-a gradient.

  6. What organism causes the most common community-acquired pneumonia, and what is its classic presentation?

    Streptococcus pneumoniae, presenting with acute fever, productive rust-colored sputum, and lobar consolidation.

  7. What is the mechanism of albuterol in asthma?

    It is a short-acting beta-2 agonist that stimulates β2 receptors, increasing cAMP and relaxing bronchial smooth muscle for bronchodilation.

  8. Trace the segments of the nephron in order from glomerulus to collecting duct.

    Bowman's capsule → proximal convoluted tubule → loop of Henle (descending and ascending) → distal convoluted tubule → collecting duct.

  9. What is the formula for net filtration pressure across the glomerulus?

    NFP = (PGC − PBS) − (πGC − πBS); driven mainly by glomerular capillary hydrostatic pressure minus Bowman's space pressure minus capillary oncotic pressure.

  10. Where does the loop diuretic furosemide act and on what transporter?

    At the thick ascending limb of the loop of Henle, inhibiting the Na⁺-K⁺-2Cl⁻ (NKCC2) cotransporter.

  11. Give the Henderson-Hasselbalch relationship used for blood pH.

    pH = 6.1 + log([HCO₃⁻] / (0.03 × PaCO₂)). pH depends on the ratio of bicarbonate to dissolved CO₂.

  12. How do you calculate the anion gap, and what defines a high gap?

    Anion gap = Na⁺ − (Cl⁻ + HCO₃⁻); normal is 8–12 mEq/L. A high anion gap metabolic acidosis is >12 (mnemonic MUDPILES).

  13. Distinguish nephritic from nephrotic syndrome.

    Nephritic: hematuria, RBC casts, hypertension, mild proteinuria (inflammatory). Nephrotic: proteinuria >3.5 g/day, hypoalbuminemia, edema, hyperlipidemia.

  14. What is the primary stimulus and action of aldosterone in the kidney?

    Stimulated by angiotensin II and hyperkalemia; it acts on the principal cells of the collecting duct to increase Na⁺ reabsorption and K⁺/H⁺ secretion.

  15. What cells secrete gastrin and what is its main action?

    G cells of the gastric antrum secrete gastrin, which stimulates parietal cell H⁺ secretion and gastric mucosal growth.

  16. What is the classic cause and location of duodenal versus gastric peptic ulcers?

    Both linked to H. pylori; duodenal ulcers are often from increased acid and pain improves with food, while gastric ulcers worsen with food and carry malignancy risk.

  17. Compare the hormones of the hypothalamic-pituitary-thyroid axis and their feedback.

    Hypothalamic TRH stimulates pituitary TSH, which stimulates thyroid T3/T4. T3/T4 provide negative feedback on TRH and TSH.

  18. Distinguish primary, secondary, and tertiary adrenal insufficiency by ACTH and cortisol.

    Primary (Addison): low cortisol, high ACTH. Secondary: low cortisol, low ACTH (pituitary). Tertiary: low cortisol, low ACTH/CRH (hypothalamic).

  19. What are the laboratory findings in type 1 diabetes mellitus ketoacidosis (DKA)?

    Hyperglycemia, high anion gap metabolic acidosis, positive serum/urine ketones, and total body potassium depletion despite possibly normal serum K⁺.

  20. Describe the hormonal events triggering ovulation in the menstrual cycle.

    Rising estrogen from the dominant follicle exerts positive feedback on the pituitary, causing an LH surge that triggers ovulation around day 14.

  21. What hormone maintains the corpus luteum in early pregnancy, and what produces it?

    Human chorionic gonadotropin (hCG), produced by the syncytiotrophoblast, maintains the corpus luteum's progesterone output.

  22. Which structure connects the two cerebral hemispheres, and what is the role of the internal capsule?

    The corpus callosum connects the hemispheres. The internal capsule carries ascending/descending projection fibers including the corticospinal tract.

  23. What is the resting membrane potential of a typical neuron, and which ion gradient dominates it?

    About −70 mV, determined primarily by the high resting permeability to K⁺ (potassium equilibrium potential).

  24. Differentiate an ischemic from a hemorrhagic stroke in mechanism.

    Ischemic stroke results from arterial occlusion (thrombotic or embolic) causing infarction; hemorrhagic stroke results from vessel rupture and bleeding into brain tissue.

  25. What is the classic CSF and MRI finding in multiple sclerosis?

    Oligoclonal IgG bands in CSF and multiple white-matter demyelinating plaques disseminated in space and time on MRI.

  26. Contrast the neurotransmitter and protein pathology of Parkinson versus Alzheimer disease.

    Parkinson: dopamine loss in substantia nigra with Lewy bodies (α-synuclein). Alzheimer: acetylcholine deficit with β-amyloid plaques and tau neurofibrillary tangles.

  27. What is the first-line drug for tonic-clonic (grand mal) status epilepticus, and its mechanism?

    Benzodiazepines (e.g., lorazepam), which enhance GABA-A receptor chloride influx, increasing inhibitory tone to terminate seizures.

  28. What enzyme is targeted by allopurinol, and in what joint disease is it used?

    Xanthine oxidase; allopurinol reduces uric acid production for chronic management of gout.

  29. Contrast osteoporosis and osteomalacia in terms of bone mineralization.

    Osteoporosis: decreased bone mass with normal mineralization. Osteomalacia: defective mineralization of osteoid, usually from vitamin D deficiency.

  30. Differentiate rheumatoid arthritis from osteoarthritis by joint involvement and pathology.

    RA: autoimmune symmetric inflammatory arthritis of MCP/PIP with pannus and morning stiffness. OA: degenerative cartilage loss in weight-bearing/DIP joints with osteophytes.

  31. Describe the coagulation cascade endpoint and the role of vitamin K.

    Both pathways converge on factor X activation, generating thrombin that converts fibrinogen to fibrin. Vitamin K is required for γ-carboxylation of factors II, VII, IX, X, and proteins C and S.

United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease FAQ

What is in the United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease syllabus?

United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease is split into 6 chapters: Cardiovascular System, Respiratory System, Renal, GI, and Endocrine Systems, Nervous System and Special Senses, Musculoskeletal, Skin, and Connective Tissue and Hematologic and Lymphoreticular System. Together they contain 30 topics and 41 sub-topics.

How many chapters are in United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease?

6 chapters, containing 30 topics and 41 sub-topics. The largest chapter is Cardiovascular System, with 5 topics.

Are there flashcards for United States Medical Licensing Examination (USMLE) Organ Systems: Structure, Function, and Disease?

Yes — a 51-card Organ Systems: Structure, Function, and Disease deck, printed in full in the flashcards section of this page and available in the Examius app with spaced repetition. The free plan covers one exam of your choice, including its flashcards; Examius Pro, a one-time purchase, unlocks every other exam and deck.