The oral cavity and oropharynx are lined by ______ epithelium.

Correct Answer: C

Rationale: The correct answer is C: stratified squamous epithelium. The oral cavity and oropharynx are exposed to mechanical stress and potential abrasion from food particles and pathogens, requiring a protective lining. Stratified squamous epithelium is ideal for providing protection due to its multiple layers of cells, with the outermost layer being flat and scale-like. This structure helps to resist damage and maintain integrity in areas of high wear and tear. Simple squamous (A) is too thin and delicate for this function. Simple columnar (B) is typically found in areas involved in absorption and secretion, not in protective roles. Stratified cuboidal (D) is rare in the body and not suited for the mechanical stress experienced in the oral cavity and oropharynx.

Correct Answer: A

Rationale: Rationale: 1. Gastrin is released by the stomach to stimulate gastric acid secretion. 2. Gastrin is also released by the small intestine to regulate digestive processes. 3. Secretin is released by the small intestine to stimulate bicarbonate secretion. 4. Cholecystokinin is released by the small intestine to stimulate bile release. 5. Gastric inhibitory polypeptide is released by the small intestine to inhibit gastric acid secretion. Summary: A: Gastrin is the correct answer as it is released by both the stomach and small intestine. B: Secretin is only released by the small intestine. C: Cholecystokinin is only released by the small intestine. D: Gastric inhibitory polypeptide is only released by the small intestine.

Correct Answer: C

Rationale: The correct answer is C because cholecystokinin inhibits gastric secretions, stimulates pancreatic secretions high in enzymes, and stimulates contraction of the gall bladder and relaxation of the sphincter of Oddi. This hormone is released in response to the presence of fats and proteins in the small intestine, leading to the digestion and absorption of these nutrients. Choices A and B are incorrect as they do not fully capture the wide range of effects of cholecystokinin. Choice D is also incorrect because it includes the stimulation of bile secretion, which is not a direct effect of cholecystokinin.

Correct Answer: C

Rationale: The correct answer is C: brush border of the small intestine. Disaccharides are broken down into monosaccharides by specific enzymes located in the brush border of the small intestine. These enzymes include sucrase, lactase, and maltase. The breakdown of disaccharides into monosaccharides occurs in the final stage of carbohydrate digestion, allowing for absorption into the bloodstream. Choices A, B, and D are incorrect because disaccharides are not primarily digested in the stomach, the lumen of the small intestine, or the colon. The main site for disaccharide digestion is the brush border of the small intestine where these specific enzymes are located.

Correct Answer: A

Rationale: The correct answer is A because the absorption of glucose is indeed associated with sodium uptake. This process occurs through the sodium-glucose cotransporter located on the apical membrane of the enterocytes in the small intestine. Sodium acts as a co-transporter, helping to facilitate the absorption of glucose. This mechanism is crucial for efficient absorption of glucose in the GI tract. Choice B is incorrect as glucose is actually absorbed more rapidly than fructose due to differences in transport mechanisms. Choice C is incorrect since galactose and fructose are absorbed by different transporters at the brush border membrane. Choice D is also incorrect because the majority of water absorption occurs in the small intestine, not the colon.