Where are most digestive enzymes secreted?

Correct Answer: C

Rationale: The correct answer is C: pancreas. The pancreas secretes most digestive enzymes, including amylase, lipase, and proteases, into the small intestine to aid in the digestion of carbohydrates, fats, and proteins. It plays a crucial role in breaking down food components. The stomach (choice A) secretes gastric juices but not the majority of digestive enzymes. The liver (choice B) produces bile, which aids in fat digestion, but does not secrete digestive enzymes. The small intestine (choice D) is where most digestion and absorption occur, but it does not secrete the majority of digestive enzymes.

Correct Answer: B

Rationale: The correct answer is B: mechanical digestion. Teeth play a crucial role in breaking down food into smaller pieces through physical chewing, which is a form of mechanical digestion. This process increases the surface area of food particles, making it easier for enzymes to further break down nutrients during chemical digestion in the stomach and intestines. Choice A (chemical digestion) is incorrect because teeth do not directly participate in chemical breakdown of food. Choice C (enzymatic digestion) is incorrect as enzymes are not produced by teeth but by salivary glands and other digestive organs. Choice D (absorption) is incorrect as teeth are not involved in absorbing nutrients; absorption primarily occurs in the small intestine.

Correct Answer: C

Rationale: The correct answer is C: Digesting proteins. Pepsin is a digestive enzyme produced in the stomach that specifically breaks down proteins into smaller peptides. It works optimally in acidic environments, aiding in the digestion of proteins consumed in the diet. The other choices are incorrect because pepsin does not play a role in digesting carbohydrates (A), fats (B), or nucleic acids (D). Carbohydrates are primarily broken down by enzymes like amylase, fats by lipase, and nucleic acids by nucleases. Thus, pepsin's main function is to digest proteins in the stomach.

Correct Answer: B

Rationale: The correct answer is B: Hyperplasia of gastric mucosal lymphocytes. In a tumor producing large amounts of gastrin, hyperplasia of gastric epithelium (choice A) is expected due to increased gastrin stimulation. Excessive gastric acid secretion (choice C) is also expected as gastrin stimulates acid production. Histamine secretion in the gastric mucosa (choice D) can occur as histamine is released in response to gastrin. However, hyperplasia of gastric mucosal lymphocytes (choice B) is not a direct consequence of increased gastrin levels. Lymphocyte hyperplasia is more commonly associated with chronic inflammation or infection rather than gastrin overproduction.

Correct Answer: B

Rationale: Secretin is the correct answer because it is not a hormone that directly affects the stomach. Gastrin stimulates gastric acid secretion, GIP enhances insulin release, and neurotensin regulates gastric motility. Secretin primarily targets the pancreas and liver, stimulating the release of bicarbonate-rich pancreatic juice. This hormone does not have a direct major effect on the stomach like the other options. Therefore, Secretin is the exception among the listed GIT hormones affecting the stomach.