Contraction of the ventricles of the heart leads to blood moving directly

Correct Answer: A

Rationale: Ventricular contraction (systole) forces blood into arteries the left ventricle into the aorta, the right into the pulmonary trunk via semilunar valves, initiating circulation. Capillaries receive blood later, after arterioles. Veins return blood to the heart, not from ventricles. Atrioventricular valves (tricuspid, mitral) close during systole, preventing backflow into atria, not directing outflow. This arterial ejection, driven by ventricular pressure, is the heart's pumping essence, key in cardiac cycle dynamics and assessing output in heart failure.

Correct Answer: A

Rationale: The foramen ovale, an atrial septal opening in fetuses, allows blood to flow from the right atrium to the left, bypassing lungs oxygen comes from the placenta via umbilical veins. Ventricular shunting isn't its role (ductus arteriosus does that). It's not a vena cava valve or aortic backflow preventer. This shunt, closing post-birth (fossa ovalis), optimizes fetal circulation, key in congenital defects like ASD where it persists, affecting oxygenation.

Correct Answer: D

Rationale: The endocardium, the heart's internal layer, is endothelium over connective tissue, lining chambers and contacting blood, distinct from epicardium (outer), myocardium (muscle), and pericardium (sac). It ensures smooth flow, key in endocarditis where infection targets it, a critical inner boundary in heart anatomy and pathology.

Correct Answer: A

Rationale: The nose (A) warms, moistens, and cleans air, per the key. Its turbinates increase surface area (150 cm²), warming air to 37°C, humidifying to 90%, and trapping particles via mucus/hairs (e.g., 10 μm filtered). The pharynx (B) conducts air/food, larynx (C) phonates, and trachea (D) conducts none match the nose's conditioning role. Physiology texts note nasal mucosa's vascularity and cilia clear 10000 L/day of air, distinguishing A from B's passageway, C's vocal function, or D's cartilage-supported conduit only the nose preps air for alveoli.

Correct Answer: C

Rationale: Enoxaparin (C) prevents pulmonary embolism (PE), per document (3). This anticoagulant (LMWH) inhibits factor Xa, reducing clot risk (e.g., 40 mg/day). Streptokinase (A) dissolves clots, not prevents. Vitamin K (B) reverses anticoagulation opposite effect. Protamine (D) counters heparin overdose. PE prophylaxis (e.g., post-surgery) relies on C's antithrombotic action 80% risk reduction unlike A's thrombolysis or B's clotting aid.