What is the primary function of the large intestine?

Correct Answer: B

Rationale: The primary function of the large intestine is to absorb water and electrolytes from the indigestible food residue passed from the small intestine. This absorption process helps in forming solid waste (feces) and maintaining body fluid balance. Absorbing nutrients (Option A) primarily occurs in the small intestine. Digesting proteins (Option C) mainly takes place in the stomach and small intestine. The secretion of digestive enzymes (Option D) also primarily occurs in the stomach and small intestine, not in the large intestine. Therefore, the correct answer is B.

Correct Answer: B

Rationale: The correct answer is B: Stomach. Protein digestion begins in the stomach where the enzyme pepsin is secreted. Pepsin breaks down proteins into smaller peptides. This process is aided by the acidic environment of the stomach. In contrast, the mouth primarily starts the digestion of carbohydrates through the enzyme salivary amylase. The small intestine is where further breakdown and absorption of nutrients occur, not the initial digestion of proteins. The large intestine is mainly responsible for absorbing water and electrolytes, not digestion.

Correct Answer: A

Rationale: The correct answer is A: It gives bile its color. Bilirubin is a pigment produced from the breakdown of hemoglobin in the liver, giving bile its characteristic yellow-green color. This is important for bile to aid in the emulsification and digestion of fats. Choices B and D are incorrect as stercobilinogen is produced from bilirubin in the intestine, contributing to stool color, not bile color. Choice C is incorrect as bile salts, not bilirubin, facilitate the absorption of lipids in the small intestine.

Correct Answer: D

Rationale: The correct answer is D because parasympathetic stimulation causes the contraction of the gall bladder. This is due to the release of acetylcholine which stimulates the gall bladder to contract and release bile into the duodenum to aid in digestion. Choices A, B, and C are incorrect as parasympathetic stimulation does not cause constriction of the pylorus, contraction of the internal anal sphincter, or contraction of the external anal sphincter.

Correct Answer: B

Rationale: The correct answer is B: congenital heterotopia. This is because the presence of small intestinal type epithelium in the gastric mucosa indicates ectopic tissue that is not normally found in the stomach. This condition is known as congenital heterotopia, where tissues from one organ are found in another due to developmental abnormalities. A: Chronic gastritis would not lead to the presence of small intestinal type epithelium in the gastric mucosa. C: Precancerous dysplasia refers to abnormal cellular changes that can progress to cancer but does not explain the presence of small intestinal type epithelium. D: Metastatic carcinoma would involve the spread of cancer cells from another primary site, not the presence of ectopic tissue.