Which of the following is not part of the large intestines?

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: 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.

Correct Answer: A

Rationale: The correct answer is A because parietal cells secrete hydrogen ions and chloride ions into the lumen, which combine to form hydrochloric acid, maintaining the acidic pH of the stomach essential for digestion. Option B is incorrect as alkaline mucous is produced by goblet cells, not parietal cells. Option C is incorrect as histamine is secreted by enterochromaffin-like cells, not parietal cells. Option D is incorrect as gastric lipase is primarily secreted by chief cells in the stomach.

Correct Answer: D

Rationale: The correct answer is D, stomach. The stomach is not considered an accessory digestive organ as it is part of the gastrointestinal tract. The accessory digestive organs aid in the digestion process but are not part of the tract itself. The tongue, liver, and pancreas are all considered accessory digestive organs as they play crucial roles in digestion, such as producing enzymes and bile. The stomach's main function is to store and break down food through mechanical and chemical digestion, making it a primary organ in the digestive system rather than an accessory one.