The partial pressure of oxygen in arterial blood is approximately

Correct Answer: B

Rationale: The correct answer is B: 100 mm Hg. In arterial blood, the partial pressure of oxygen is typically around 100 mm Hg due to the oxygen-rich environment in the lungs. This value represents the pressure exerted by oxygen molecules in the blood. Choices A, C, and D are incorrect because they do not align with the normal range of oxygen partial pressure in arterial blood, which is around 100 mm Hg. Option A is too low, option C is slightly below the normal range, and option D is slightly above the normal range. Therefore, B is the most accurate representation of the typical partial pressure of oxygen in arterial blood.

Correct Answer: C

Rationale: The correct answer is C because vital capacity actually decreases with age due to changes in lung elasticity and muscle strength. A is correct as aging causes the lungs to lose elastic tissue. B is correct as lung compliance changes with age. D is correct as respiratory muscles weaken over time. Therefore, only option C is false in the context of age-related changes in lung function.

Correct Answer: C

Rationale: The correct answer is C: Left ventricle. The left ventricle is the chamber responsible for pumping oxygenated blood to the rest of the body, making it the most commonly affected in heart failure. When the left ventricle weakens or becomes stiff, it can lead to inefficient pumping, causing fluid buildup and symptoms of heart failure. The other choices, A: Left atrium, B: Right atrium, and D: Right ventricle, are less commonly affected in heart failure as they have different functions in the heart's circulation.

Correct Answer: B

Rationale: During expiration, the diaphragm relaxes, causing it to move upwards, which decreases the thoracic space. This leads to the expulsion of air from the lungs. In contrast, during inspiration, the diaphragm contracts and moves downwards, increasing the thoracic space to allow air to enter the lungs. Option C, Pause, does not involve any specific respiratory phase. Option D, both a and b, is incorrect because during inspiration, the diaphragm contracts and increases thoracic space. Therefore, the correct answer is B, expiration, as this phase specifically involves the relaxation of the diaphragm and the decrease in thoracic space.

Correct Answer: B

Rationale: The correct answer is B: horn shape. The corniculate cartilages are small, horn-shaped structures located on the apex of the arytenoid cartilages in the larynx. These cartilages play a role in supporting the vocal folds. The other choices (A, C, D) are incorrect because the corniculate cartilages are not club-shaped, bate-shaped, or butterfly-shaped. It is crucial to understand the anatomical structure and function of the corniculate cartilages to identify the correct shape accurately.