Bile production by the liver cells is increased by:

Correct Answer: C

Rationale: The correct answer is C: CCK. Cholecystokinin (CCK) is a hormone released by the small intestine in response to the presence of fatty acids and amino acids. It stimulates the release of bile from the gallbladder and increases bile production by the liver cells to aid in digestion. Sympathetic activation (choice A) typically inhibits digestive functions. Secretin (choice B) primarily stimulates pancreatic bicarbonate secretion, not bile production. Bile salts (choice D) are products of bile, not direct stimulators of bile production. Therefore, CCK is the correct choice as it directly influences the production of bile by the liver cells.

Correct Answer: A

Rationale: Saliva contains an enzyme called amylase, which helps break down sucrose (a type of sugar) into glucose and fructose for digestion. Therefore, the correct answer is A. Saliva does not play a significant role in the digestion of phospholipids (B), speaking ability (C), or breaking food down into small pieces (D).

Correct Answer: B

Rationale: The correct answer is B because the small intestine has a larger internal surface area compared to the large intestine due to its extensive folding and villi. This increased surface area enhances nutrient absorption efficiency. Choice A is incorrect as the small intestine is longer than the large intestine. Choice C is incorrect as the small intestine absorbs more water than the large intestine. Choice D is incorrect as the small intestine typically does not contain the same amount of bacteria as the large intestine, which is known for its significant bacterial population.

Correct Answer: D

Rationale: The correct answer is D because peristalsis, a coordinated muscle contraction that propels food along the gastrointestinal tract, is indeed seen in most parts of the GIT. This process helps move food from the esophagus to the stomach, and then throughout the intestines for digestion and absorption. Peristalsis is essential for the proper functioning of the digestive system. Choice A is incorrect because gastrointestinal motility is regulated by both neural and hormonal factors. Choice B is incorrect as the emptying of the stomach is mainly facilitated by the rhythmic contractions of the stomach muscles, not segmentation contractions. Choice C is incorrect as the movement of chyme along the small intestine is primarily due to segmentation and peristalsis, not the migrating motor complex.

Correct Answer: B

Rationale: The submucosa of the GIT is rich in blood vessels, nerves, and lymphatic vessels, aiding in absorption and secretion of nutrients and fluids. The submucosa is not primarily responsible for protection (choice A). It does not contain distinct outer and inner layers (choice C). The submucosa is located between the mucosa and muscularis externa, not the serosa (choice D). Therefore, the correct answer is B as it aligns with the known functions and characteristics of the submucosa.