The functions of the colon include the following except:

Correct Answer: D

Rationale: The correct answer is D: Absorption of calcium. The colon primarily absorbs water, sodium, and chloride, but not calcium. Calcium absorption mainly occurs in the small intestine. The colon's main function is to absorb water and electrolytes, and to store and eliminate waste. Therefore, absorption of calcium does not occur in the colon, making choice D the correct answer. Choices A, B, and C are incorrect as the colon is involved in the absorption of water, sodium, and chloride, respectively.

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.

Correct Answer: C

Rationale: The correct answer is C because dysphagia, which is difficulty swallowing, can be caused by various factors such as neurological disorders affecting the swallowing reflex or physical obstructions in the esophagus. This is a key point in understanding the causes of swallowing difficulties. Choice A is incorrect because the pharyngeal phase of swallowing is actually involuntary, not voluntary. Choice B is incorrect as the lower esophageal sphincter (LES) is normally closed to prevent acid reflux and only opens during swallowing. Choice D is incorrect because in the esophageal stage of swallowing, both liquid and solid boluses travel through the esophagus by peristalsis, not just liquid boluses.