Esophageal glands are located:

Correct Answer: B

Rationale: Esophageal glands are located in the submucosa because they secrete mucus to aid in swallowing. The submucosa is the layer beneath the mucosa where glands are typically found. The mucosa is the innermost layer responsible for absorption and protection. The serosa is the outermost layer providing a smooth surface for movement. The adventitia is a connective tissue layer that supports and attaches organs. Therefore, the correct answer is B because esophageal glands are located in the submucosa to facilitate swallowing.

Correct Answer: B

Rationale: The correct answer is B: chief (zymogenic) cells. These cells are responsible for secreting pepsinogen, which is the inactive form of pepsin, an enzyme that helps in the digestion of proteins in the stomach. Goblet cells (A) secrete mucus, parietal (oxyntic) cells (C) secrete hydrochloric acid, and Kupffer cells (D) are found in the liver and are involved in immune function, not in stomach digestion. Therefore, the correct choice is chief (zymogenic) cells as they specifically secrete pepsinogen for protein digestion in the stomach.

Correct Answer: D

Rationale: The correct answer is D because cells lining the sides of intestinal crypts of Lieberkühn are responsible for supplying replacement cells for the epithelium of villi. These cells undergo rapid division and differentiation to replace the cells shed from the villi, ensuring the continuous renewal and maintenance of the intestinal lining. This process is crucial for the absorption of nutrients and maintaining the integrity of the intestinal barrier. Choice A (secreting digestive enzyme) is incorrect because the cells in the intestinal crypts primarily function in cell replacement, not enzyme secretion. Choice B (secreting one of several various hormones) is incorrect as the main function of these cells is not hormone secretion but rather cell turnover. Choice C (secreting mucus) is incorrect as mucus secretion is typically associated with other specialized cells in the intestinal lining, such as goblet cells, not the cells in the crypts responsible for cell replacement.

Correct Answer: D

Rationale: Absorptive epithelial cells of the small intestine (enterocytes) are characterized by: A: Apical brush border composed of microvilli - This increases surface area for absorption. B: A glycocalyx containing various digestive enzymes - This aids in digestion and absorption. C: Junctional complexes including tight junctions separating apical from lateral cell membranes - This maintains cell polarity and regulates permeability. Therefore, choice D is correct as all these characteristics are typical of absorptive epithelial cells in the small intestine.

Correct Answer: B

Rationale: The correct answer is B: central vein. The hepatic lobule is a structural unit of the liver, consisting of hepatocytes arranged in a hexagonal pattern around a central vein. Hepatocytes receive oxygenated blood from the hepatic artery and nutrient-rich blood from the portal vein. These blood vessels merge within the lobule, and the blood flows towards the central vein. Bile produced by hepatocytes drains into bile canaliculi and eventually into bile ducts, which are not directly associated with defining the hepatic lobule. Therefore, the central vein is the correct answer as it is the vessel that receives blood from the sinusoids in the lobule.