Through which structure does blood pass from the right atrium to the right ventricle?

Correct Answer: C

Rationale: The tricuspid valve allows blood to pass from the right atrium to the right ventricle, opening during diastole and closing during systole to prevent backflow its three cusps ensure one-way flow. The bicuspid (mitral) valve serves the left side. The interventricular septum separates ventricles, not a passage. The mitral valve is left-sided, not right. Named for its three leaflets, the tricuspid's role is pivotal in right heart circulation, a fundamental valve in cardiac flow, critical in conditions like tricuspid regurgitation affecting pulmonary return.

Correct Answer: B

Rationale: The T wave on an ECG represents ventricular repolarization, when potassium exits cells, relaxing the myocardium after systole key to resetting for the next beat. The R wave, part of the QRS complex, shows ventricular depolarization and contraction. The S wave completes QRS, not repolarization. The P wave is atrial depolarization. The T wave's shape and timing reflect recovery, critical in diagnostics e.g., inverted T waves signal ischemia making it a cornerstone of ECG interpretation and cardiac health assessment.

Correct Answer: D

Rationale: The pericardium, a saclike structure, encases the heart fibrous pericardium anchors it, serous layers (parietal, visceral/epicardium) reduce friction. The epicardium is the heart's outer layer within this sac, myocardium the muscle, endocardium the inner lining. This sac's dual role protection, lubrication is vital, key in pericardial diseases like tamponade, a fundamental cardiac enclosure in anatomy.

Correct Answer: D

Rationale: Internal respiration (D) is the O₂ and CO₂ exchange between blood and tissue cells, per the key. Pulmonary ventilation (A) moves air into lungs (e.g., 6-8 L/min at rest). External respiration (B) occurs in alveoli. Transport of respiratory gases (C) is blood-mediated (e.g., 98% O₂ on Hb). At tissues, O₂ unloads (PvO₂ ≈40 mmHg) to cells, and CO₂ (PvCO₂ ≈46 mmHg) enters blood, per Bohr effect (pH shift). This cellular gas swap vital for metabolism (e.g., 250 mL/min O₂ use) defines D, contrasting with A's airflow, B's lung focus, or C's transit role, making internal respiration the tissue-specific process.

Correct Answer: A

Rationale: Alpha-1-antitrypsin (AAT) deficiency (A) causes early COPD (document: 1), per ATS 1% of cases, onset <40 years. AAT protects alveoli from elastase; deficiency (e.g., ZZ genotype) yields panacinar emphysema. Childhood smoking (B) or secondhand smoke (C) accelerates COPD but typically later (50s). Smokeless tobacco (D) affects oral health, not lungs. A's genetic basis AAT <11 μmol/L explains rapid destruction (FEV₁ <50%), distinguishing it from B's or C's environmental latency.