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

Organ Systems: Structure, Function, and Disease syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Organ Systems: Structure, Function, and Disease in United States Medical Licensing Examination (USMLE), not a summary of it.

1. 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. 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. 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. 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. 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. 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

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

21 of 51 cards from the Organ Systems: Structure, Function, and Disease deck — real questions with worked 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.

21. 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).

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