What is the function of the pleurae?

Correct Answer: A

Rationale: The pleurae play a crucial role in compartmentalizing and lubricating the lungs. The pleura is a double-layered membrane that surrounds the lungs and lines the chest cavity. This double-layered structure reduces friction between the lungs and the chest wall during breathing movements, allowing smooth expansion and contraction of the lungs. Options B, C, and D are incorrect. Option B, 'To facilitate the flow of air,' is incorrect because while the pleurae are involved in the respiratory process, their primary function is not to directly facilitate the flow of air. Option C, 'To produce mucus,' is incorrect as the production of mucus is not a primary function of the pleurae. Option D, 'To serve as the passageway for air,' is incorrect as the passageway for air refers to the air passages like the trachea and bronchi, not the pleurae. Therefore, option A is correct as it accurately describes the function of the pleurae.

Correct Answer: D

Rationale: The correct answer is D, 'All of the above.' When viewed from an anterior perspective, the left common carotid artery, pulmonary trunk, and subclavian arteries all carry blood away from the heart. The left common carotid artery supplies oxygenated blood to the head and neck, the pulmonary trunk carries deoxygenated blood to the lungs for oxygenation, and the subclavian arteries transport blood to the upper extremities. Therefore, all the vessels listed in the choices are correct as they function to carry blood away from the heart when viewed anteriorly.

Correct Answer: B

Rationale: The correct answer is B because the heartbeat actually begins when the heart muscles relax, allowing the chambers to fill with blood. The contraction phase follows, which propels blood out of the heart. The other statements are accurate in describing the normal sequence of events in the heart's functioning: the atria contract to push blood into the ventricles, the valves close to prevent backflow of blood, and the ventricles contract to pump blood out of the heart.

Correct Answer: D

Rationale: The correct answer is D: Villi. Villi are small, finger-like projections in the small intestine that increase the surface area for absorption, aiding in the absorption of nutrients. Cilia (Choice A) are tiny hair-like structures found in various parts of the body but are not present in the small intestine. Rugae (Choice B) are folds in the mucosa of the stomach that allow for its expansion during digestion. The trachea (Choice C) is part of the respiratory system, responsible for carrying air to and from the lungs, and is not related to the small intestine.

Correct Answer: D

Rationale: The correct answer is Polymerase. Polymerase is the enzyme responsible for adding nucleotides to a growing DNA chain during DNA replication. Helicase unwinds the DNA double helix to separate the DNA strands for replication, Ligase joins DNA fragments together by catalyzing the formation of phosphodiester bonds between them, and Nuclease cuts or degrades DNA strands. Therefore, choices A, B, and C are incorrect in the context of adding nucleotides to a growing DNA chain.