Which of the following structures protects the lower respiratory system from food and fluid bolus during swallowing?

Correct Answer: B

Rationale: The correct answer is B: epiglottis. The epiglottis is a flap of tissue that covers the opening of the trachea during swallowing, preventing food and fluid from entering the lower respiratory system. This mechanism ensures that the airway remains clear and protects the lungs from aspiration. The other choices are incorrect because: A: The larynx is involved in sound production and air passage but does not specifically protect the lower respiratory system during swallowing. C: The vestibule is the space within the nasal cavity but does not play a direct role in protecting the lower respiratory system during swallowing. D: The pharynx is a passageway for both food and air but does not specifically prevent food and fluid bolus from entering the lower respiratory system during swallowing.

Correct Answer: B

Rationale: The correct answer is B: carbon dioxide. Carbon dioxide is the most important chemical regulator of respiration as it directly affects the respiratory rate and depth. An increase in carbon dioxide levels in the blood triggers the body to increase respiration to expel the excess carbon dioxide. Conversely, a decrease in carbon dioxide levels signals the body to decrease respiration. Oxygen (choice A) is important for cellular respiration but does not directly regulate breathing. Bicarbonate ion (choice C) and sodium ion (choice D) do not play a direct role in regulating respiration.

Correct Answer: D

Rationale: The correct answer is D, pseudostratified ciliated columnar epithelium. This type of epithelium lines the conducting portion of the respiratory tract because it contains cilia that help sweep mucus and debris out of the airways. It appears to be stratified but is actually a single layer of cells with varying heights, giving it a pseudostratified appearance. Simple squamous epithelium (choice A) is too thin for the respiratory tract, simple columnar epithelium (choice B) lacks cilia for mucus clearance, and stratified ciliated columnar epithelium (choice C) is not a valid type of epithelium.

Correct Answer: C

Rationale: The correct answer is C: Beta-blockers. Beta-blockers are commonly prescribed in heart failure to manage symptoms and improve outcomes by reducing the heart's workload and improving its efficiency. They help lower blood pressure, decrease heart rate, and improve heart function. Antibiotics (A) are used to treat bacterial infections, not heart failure. Antidepressants (B) are used for mental health conditions, not heart failure. Antihistamines (D) are used to treat allergies, not heart failure.

Correct Answer: A

Rationale: The correct answer is A: septal cells. Type 2 alveolar cells are also known as septal cells because they are located in the alveolar septa. These cells are responsible for producing and secreting surfactant, a substance that helps reduce surface tension in the alveoli and prevents them from collapsing. Choice B, petal cells, is incorrect because there is no such term used to describe these cells. Choice C, Surfactant, is incorrect because surfactant is the substance produced by type 2 alveolar cells, not the name of the cells themselves. Choice D, respiratory cell, is incorrect because it is a vague term that does not specifically refer to type 2 alveolar cells.