Which of these statements about the pharynx is true?

Correct Answer: B

Rationale: The correct answer is B because the oropharynx is indeed continuous superiorly with the nasopharynx, forming a passage for both air and food. This continuity allows for the passage of food and air between the oral and nasal cavities. A is incorrect because the pharynx extends from the nasal and oral cavities superiorly to the esophagus posteriorly, not anteriorly. C is incorrect because the nasopharynx is not involved in digestion; it primarily functions in respiration and contains the openings of the Eustachian tubes. D is incorrect because the laryngopharynx is not composed partially of cartilage; it is a muscular passage that connects the oropharynx and the esophagus.

Correct Answer: C

Rationale: The correct answer is C: hydrochloric acid. Hydrochloric acid is responsible for creating an acidic environment in the stomach essential for the activation of pepsin and the breakdown of proteins into peptides. This acidic environment also helps in the denaturation of proteins and kills harmful bacteria present in food. Bile (choice A) aids in digestion of fats in the small intestine. Mucus (choice B) helps protect the stomach lining from the acidic environment. Pepsin (choice D) is an enzyme that breaks down proteins but is activated by hydrochloric acid.

Correct Answer: B

Rationale: The correct answer is B: bile. The liver secretes bile to aid in digestion by emulsifying fats, helping in their breakdown and absorption. Insulin (choice A) is secreted by the pancreas to regulate blood sugar levels, not aid in digestion. Gastrin (choice C) is a hormone produced by the stomach to stimulate the secretion of gastric acid, not by the liver. Pepsin (choice D) is an enzyme produced in the stomach to break down proteins, not secreted by the liver.

Correct Answer: B

Rationale: The colon's main role in digestion is the absorption of water and electrolytes from undigested food, forming feces. This process helps maintain body fluid balance. The other choices are incorrect because: A) Carbohydrates are primarily digested in the small intestine. C) Bile is produced in the liver and stored in the gallbladder, aiding in fat digestion in the small intestine. D) Enzymes are secreted in the stomach and small intestine to aid in digestion, not in the colon.

Correct Answer: B

Rationale: The correct answer is B: Large intestine. The large intestine is responsible for the absorption of water and electrolytes from the remaining indigestible food matter that passes through the small intestine. It reabsorbs water and electrolytes to maintain the body's fluid balance. The small intestine primarily absorbs nutrients and vitamins, while the stomach is responsible for the initial digestion of food and the pancreas secretes digestive enzymes into the small intestine. Therefore, the large intestine is the correct choice for water and electrolyte absorption in the digestive system.