Anatomy, Physiology, and Disease Processes
The Anatomy, Physiology, and Disease Processes domain tests structural and functional relationships, directional terminology, and the mechanisms behind common disorders. Questions often ask you to link a symptom pattern to an organ system or to distinguish similar disease processes.
Core rules
- Use anatomical position: standing upright, palms forward. Directional pairs: anterior/ventral vs posterior/dorsal, superior vs inferior, medial vs lateral, proximal vs distal, superficial vs deep, ipsilateral vs contralateral.
- Body organization: cells, tissues, organs, systems. Major cavities are cranial, spinal, thoracic (pleural, pericardial, mediastinum), and abdominopelvic; the abdomen is divided into four quadrants or nine regions.
- Homeostasis depends on negative feedback (thermoregulation, blood glucose) and, less commonly, positive feedback (labor, clotting).
- Disease mechanisms include inflammation (rubor, calor, tumor, dolor, loss of function), infection, neoplasia (benign vs malignant, invasion, metastasis), ischemia and infarction, thrombosis and embolism, edema, hypertrophy, hyperplasia, atrophy, metaplasia, autoimmune attack, and genetic mutation.
- System anchors: SA node and cardiac cycle; ventilation/perfusion matching and acid-base balance; nephron filtration and reabsorption; endocrine feedback (thyroid, adrenal, pancreatic); neurotransmitter and reflex pathways; bone remodeling and muscle antagonism.
Worked example
A patient reports exertional dyspnea, orthopnea, paroxysmal nocturnal dyspnea, jugular venous distention, bibasilar crackles, and dependent edema. Exertional dyspnea, orthopnea, and crackles point to pulmonary congestion from left heart failure, while JVD and peripheral edema reflect systemic venous congestion from right heart failure. The combined picture suggests biventricular failure. Knowing that the left heart receives oxygenated blood from the lungs and the right heart pumps deoxygenated blood to the lungs explains why left-sided failure produces pulmonary symptoms first.
Traps
Do not reverse afferent (toward) and efferent (away). Keep systolic (ventricular contraction) and diastolic (ventricular relaxation) distinct. Left heart failure is not the same as right heart failure, and cor pulmonale is right-sided. Differentiate respiratory acidosis from alkalosis by PaCO2 direction, and metabolic acidosis from alkalosis by bicarbonate. Do not confuse staging (extent of tumor) with grading (cell differentiation), or dyspnea (breathing) with dysphagia (swallowing).