Which of these structures is found in the small intestine?

Correct Answer: A

Rationale: The correct answer is A: Villi. Villi are finger-like projections lining the small intestine that increase surface area for nutrient absorption. This structure is crucial for efficient digestion and absorption of nutrients. The other choices are incorrect because: B: Hepatic portal vein - This structure is not found in the small intestine but connects the intestines to the liver. C: Goblet cells - While present in the small intestine, they are not a defining structure of the small intestine. D: Mesenteries - These are connective tissues that support and hold organs in place, not a structure specific to the small intestine.

Correct Answer: A

Rationale: The correct answer is A: Digestive enzymes. The liver produces bile, which contains bile salts that help digest fats in the small intestine. Additionally, the liver produces various digestive enzymes like lipase, amylase, and proteases. These enzymes aid in breaking down carbohydrates, proteins, and fats during the digestion process. Choices B, C, and D are incorrect because secondary bile acids are produced in the intestine, stercobilinogen is a product of bilirubin breakdown in the intestine, and CCK (cholecystokinin) is a hormone produced by the small intestine to stimulate the release of bile and pancreatic enzymes but not directly produced by the liver.

Correct Answer: D

Rationale: The correct answer is D: Duodenum. The duodenum is the first part of the small intestine, not the large intestine. The transverse colon, appendix, and cecum are all parts of the large intestine. The duodenum plays a crucial role in the digestion process, receiving partially digested food from the stomach and further breaking it down with the help of enzymes from the pancreas and bile from the liver. It is important to differentiate between the small and large intestines to understand their distinct functions within the digestive system.

Correct Answer: B

Rationale: The correct answer is B: pseudomembranous enterocolitis. Mucosal necrosis is a key characteristic of pseudomembranous enterocolitis, a condition caused by Clostridium difficile infection. The bacteria release toxins that lead to inflammation and damage to the mucosal lining of the intestines, resulting in mucosal necrosis. Blind loop syndrome (choice A) does not specifically involve mucosal necrosis, while pseudomembranous enterocolitis (choice B) does. Choice C is incorrect because only pseudomembranous enterocolitis involves mucosal necrosis. Choice D is incorrect as pseudomembranous enterocolitis does involve mucosal necrosis.

Correct Answer: D

Rationale: The correct answer is D because the stomach secretes intrinsic factor, which is essential for vitamin B12 absorption in the small intestine. This is crucial for preventing vitamin B12 deficiency and maintaining neurological health. The other choices are incorrect because A is partially true but not the main function of the stomach, B is false as total vagus nerve cut decreases stomach secretion, and C is false as the stomach pH varies from acidic (around 1.5-3.5) depending on food intake.