Which one of the connective tissue sheets listed below consists of two layers of serous membranes with a thin layer of connective tissue between them and attaches to the small intestine?

Correct Answer: B

Rationale: The correct answer is B: mesentery proper. The mesentery proper consists of two layers of serous membranes with a thin layer of connective tissue between them, and it attaches to the small intestine. This structure provides support and allows for movement of the small intestine. A: The lesser omentum attaches the stomach to the liver, not the small intestine. C: The greater omentum is a large apron-like structure that hangs down from the stomach and covers the intestines, but it does not specifically attach to the small intestine. D: The falciform ligament attaches the liver to the diaphragm and anterior abdominal wall, not the small intestine.

Correct Answer: D

Rationale: The correct answer is D: sublingual gland. This gland primarily produces mucus, aiding in lubrication and initial digestion. The sublingual gland is located under the tongue. A: The parotid gland primarily produces serous saliva. B: Labial glands are minor salivary glands located in the lips, producing mixed saliva. C: Submandibular gland produces a mixture of serous and mucous saliva.

Correct Answer: A

Rationale: The correct answer is A: gastric pits. Gastric pits are invaginations in the stomach lining that contain specialized cells for secretion of gastric juices. These pits increase the surface area of the stomach by providing a larger area for nutrient absorption and digestion. Plicae circulares are folds in the small intestine, not the stomach. Villi and microvilli are found in the small intestine and further increase surface area for absorption, not in the stomach.

Correct Answer: B

Rationale: The correct answer is B because the low pH of the stomach activates pepsin, an enzyme that digests proteins, while inactivating salivary amylase, an enzyme that digests starch. Pepsin works optimally in an acidic environment, breaking down proteins into peptides. Salivary amylase, on the other hand, works best at a neutral pH and is denatured in the acidic stomach, leading to its inactivation. Choices A, C, and D are incorrect because lipids are primarily digested in the small intestine, and nucleic acids are not directly affected by the stomach's pH.

Correct Answer: A

Rationale: The correct answer is A: lacteals. Lacteals are specialized lymphatic capillaries found in the villi of the small intestine that absorb dietary fats and fat-soluble vitamins. They play a crucial role in the transport of these nutrients to the bloodstream. Peyer's patches (B) are lymphoid nodules in the small intestine involved in immune responses. Crypts of Lieberkuhn (C) are intestinal glands that secrete digestive enzymes. Microvilli (D) are small projections on the surface of intestinal cells that increase surface area for nutrient absorption but are not lymphatic capillaries.