What is the main role of the stomach?

Correct Answer: C

Rationale: The main role of the stomach is the digestion of proteins. Step 1: Stomach secretes gastric juices containing pepsin and hydrochloric acid. Step 2: Proteins are broken down into peptides and amino acids. Step 3: These smaller molecules are then further digested and absorbed in the small intestine. Absorption of nutrients (A) primarily occurs in the small intestine, not the stomach. Bile is produced in the liver and stored in the gallbladder, not secreted by the stomach (B). The transport of food (D) occurs through the esophagus and into the stomach, not the main role of the stomach itself.

Correct Answer: D

Rationale: The correct answer is D, bile salts. The jejunum is primarily responsible for the absorption of nutrients like glucose, amino acids, and fatty acids. Bile salts are mainly absorbed in the ileum, the part of the small intestine that follows the jejunum. Bile salts aid in the digestion and absorption of fats, but they are not absorbed in the jejunum. Therefore, the jejunum is not the main site for absorption of bile salts. This makes option D the correct answer.

Correct Answer: D

Rationale: The correct answer is D because the pharyngeal phase of swallowing involves the contraction of the pharyngeal constrictors, which propel the bolus of food or liquid down the pharynx towards the esophagus. This muscular contraction helps in the proper movement of the swallow. A, a deep breath, is not part of the pharyngeal phase but may precede swallowing. B, elevation of the tongue against the hard palate, is part of the oral phase of swallowing, not the pharyngeal phase. C, contraction of the upper esophageal sphincter, occurs in the esophageal phase, not the pharyngeal phase.

Correct Answer: D

Rationale: The correct answer is D: Bicarbonate ions. Acinar cells in the exocrine pancreas are responsible for secreting digestive enzymes, which are stimulated by secretin, CCK, and parasympathetic stimulation. Bicarbonate ions, on the other hand, are secreted by ductal cells in the pancreas to neutralize the acidic chyme entering the small intestine. Therefore, an increase in bicarbonate ions would not directly affect the secretion of acinar cells. Secretin stimulates the release of bicarbonate ions, while CCK and parasympathetic stimulation trigger the release of digestive enzymes. So, choice D is the correct answer because it does not directly increase the secretion of acinar cells within the exocrine pancreas.

Correct Answer: B

Rationale: The correct answer is B: lower gastrointestinal bleeding. Hematochezia refers to the passage of bright red blood in the stool, typically originating from the lower gastrointestinal tract. Upper gastrointestinal bleeding would present as melena (dark, tarry stool). Choice A is incorrect as hematochezia does not indicate upper GI bleeding. Choice C is incorrect because hematochezia specifically points to lower GI bleeding. Choice D is incorrect as hematochezia is associated with lower GI bleeding.