Intestinal motility is increased by
**Core Concept**
Intestinal motility refers to the rhythmic contractions of the intestinal muscles that propel food through the digestive tract. The movement of intestinal contents is regulated by a complex interplay of neural, hormonal, and local factors.
**Why the Correct Answer is Right**
The correct answer is related to the release of a hormone that stimulates intestinal motility. Cholecystokinin (CCK) is a hormone released by the duodenum in response to fat and protein ingestion. CCK acts on the intestinal smooth muscle to increase contractility and enhance propulsion of intestinal contents. This hormone plays a crucial role in the regulation of intestinal motility, especially during the postprandial period.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect as it refers to a hormone that inhibits intestinal motility, rather than increasing it. Secretin is a hormone released by the duodenum in response to acid and fat ingestion, which acts to slow down intestinal motility and promote pancreatic and biliary secretions.
* **Option B:** This option is incorrect as it refers to a neurotransmitter that inhibits intestinal motility. Vagal tone, mediated by the release of acetylcholine, can slow down intestinal motility, especially in the small intestine.
* **Option C:** This option is incorrect as it refers to a condition that impairs intestinal motility. Diabetic gastroparesis is a complication of diabetes characterized by delayed gastric emptying and impaired intestinal motility.
**Clinical Pearl / High-Yield Fact**
Remember that the postprandial release of CCK is a key regulator of intestinal motility, and its deficiency or impaired release can lead to symptoms of delayed gastric emptying and postprandial bloating.
**Correct Answer: D. Cholecystokinin.**