Which one of the following is correct regarding larynx?

Correct Answer: D

Rationale: The larynx is multifunctional: it houses vocal cords for sound, its epiglottis prevents pathogens and food from entering the trachea during swallowing, and its cartilaginous structure (e.g., thyroid cartilage) connects the pharynx to the trachea, forming the airway's gateway. All statements are true. It filters air via mucus and reflexes like coughing, while its cartilage ensures patency. This triple role phonation, protection, conduction makes it a respiratory linchpin, vital in speech and airway defense, a comprehensive view essential for understanding laryngeal anatomy and clinical issues like laryngitis or choking.

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: B

Rationale: Systole is the cardiac cycle phase when a chamber (atria or ventricles) contracts, raising pressure to eject blood ventricular systole pushes blood into the aorta/pulmonary trunk. Filling occurs during diastole, when chambers relax and fill. Repolarization is an electrical event, not a mechanical phase. Diastole is relaxation, opposite to contraction. Systole's pressure rise, peaking at ~120 mmHg in the left ventricle, drives circulation, a core concept in the cardiac cycle, critical in understanding blood flow dynamics and conditions like systolic dysfunction.

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.