Which of the following lymphocytes are involved in innate immunity?

Correct Answer: A

Rationale: Natural killer (NK) cells are involved in innate immunity as they are able to directly kill virus-infected cells and tumor cells without prior sensitization. They are part of the body's first line of defense against infections. Plasma cells, CD8 T cells, and B memory cells are all part of adaptive immunity, which involves a specific response to pathogens and requires prior exposure. Therefore, they are not involved in innate immunity.

Correct Answer: C

Rationale: The correct answer is C (75 percent) because under quiet conditions, the venous blood returning to the heart still contains a significant amount of oxygen due to the efficient extraction of oxygen by tissues. This oxygen extraction process typically leaves around 25 percent of oxygen in the venous blood, which is then returned to the heart. Choices A (25 percent), B (50 percent), and D (90 percent) are incorrect because they do not accurately reflect the amount of oxygen retained in the blood under quiet conditions. Option A (25 percent) is the amount typically extracted by tissues, so it cannot be the correct answer. Option B (50 percent) is too high, as more oxygen is extracted by tissues. Option D (90 percent) is also too high, as it overestimates the amount of oxygen retained in venous blood.

Correct Answer: B

Rationale: The correct answer is B: a drop in tidal volume. Severing sensory fibers from the lungs would lead to decreased feedback to the brain, resulting in less inhibition of the inspiratory center and potentially overinflation of the lungs (choice C). The Hering-Breuer reflexes, responsible for preventing lung over-inflation, would disappear (choice D). However, tidal volume is primarily controlled by the respiratory muscles and respiratory center in the brain, not solely by sensory input from the lungs. Hence, severing sensory fibers would not directly lead to a drop in tidal volume.

Correct Answer: A

Rationale: The correct answer is A: pulmonary. The pulmonary circulation involves the flow of blood between the heart and the lungs. In this circulation, deoxygenated blood from the body is pumped to the lungs to pick up oxygen and release carbon dioxide. The oxygenated blood is then returned to the heart to be pumped to the rest of the body. The other choices (B: interlobular, C: respiratory, D: bronchial) are incorrect because they do not specifically refer to the circulation responsible for oxygenating blood and removing carbon dioxide in the lungs. Instead, they relate to other structures or functions within the respiratory system.

Correct Answer: B

Rationale: Emphysema is the correct answer because it is a chronic respiratory disorder specifically caused by smoking. Smoking damages the air sacs in the lungs, leading to shortness of breath and difficulty breathing. Asthma is a separate condition involving airway inflammation. Respiratory alkalosis and acidosis refer to imbalances in blood pH levels, not directly caused by smoking.