LECTURE 6

Gastric Motility

The process of regulating the movement of the stomach and intestines to maximize the absorption of nutrients necessary for energy and tissue maintenance.

Enteric Nervous System

A network of nerves within the gastrointestinal tract that controls motility, secretion, and blood flow independently of the central nervous system.

Slow Waves

Intrinsic electrical activity in smooth muscle cells of the GI tract that generates resting tone and can be modified to cause contractions.

Interstitial Cells of Cajal

Pacemaker cells in the gut that generate slow waves and coordinate smooth muscle contractions.

Gastrointestinal Hormones

Chemical messengers secreted by endocrine cells in the GI tract that regulate motility, secretion, and other functions in the digestive system.

Enteroendocrine cells

Cells in the gastrointestinal tract epithelium that sense specific chemicals in the lumen and respond to microbiota, producing hormones to regulate gut functions.

Chromaffin cells

A type of enteroendocrine cell that secretes serotonin (5-HT) and other hormones like CCK and secretin in response to distention and chemical stimuli.

Piezo channel

A calcium channel with mechanosensory properties discovered in 2021, important for sensing distention in the gut and triggering calcium influx leading to exocytosis.

Paracrine factors

Hormones like histamine and prostaglandins that act locally in the gastrointestinal tract, influencing functions such as acid secretion, mucus production, and motility.

Oral stage swallowing

The voluntary phase of swallowing where food is pushed to the back of the throat by the tongue and onto the palate before entering the esophagus.

Peristalsis

Coordinated contractions of the esophagus and intestines that propel food forward, including the pharyngeal and esophageal phases of swallowing and movement in the small intestine.

Segmentation

Contraction of circular muscles in the small intestine that mix and segment food, aiding in absorption and controlled by the basic electrical rhythm and local reflexes.

Ileocecal valve

A sphincter between the ileum and cecum that regulates the passage of food from the small to the large intestine, preventing backflow and controlling movement through the GI tract.

Segmentation

A type of movement in the large intestine involving strong contractions of circular muscles that pinch off segments of the intestine for water and salt removal.

Taenia coli

Three strips of longitudinal muscle in the large intestine that help in the pinching off process during segmentation.

Mass movement

A type of peristalsis in the descending colon that propels chyme over a long distance in the large intestine, occurring about three to four times per day.

Rectum

The end of the large intestine where undigested material is stored before defecation, controlled by internal and external sphincters.

Defecation reflex

The process involving short and long reflexes that lead to the expulsion of feces from the rectum through the anus.

Total Transit Time

The duration taken for food to pass through the entire gastrointestinal tract, ranging from 10 to 68 hours.

Migrating Motor Complex

A series of contractions in the stomach and small intestine that occur between meals to clear out debris, renew cells, and prevent bacterial movement, influenced by hormones like motilin.

Enteric Nervous System

The system regulating gut motility, influenced by the autonomic nervous system, and composed of slow waves induced by pacemaker cells like interstitial cells of Cajal.