Movement of GIT (2) [Intestines].pptx

Intestinal Movements and Regulation By Dr. Hira Attique Department of Physiology Overview Movements of small intestine and its regulation Ileocecal valve and ileo-cecal sphincter Movements of colon and its regulation General Principal Of GIT Functions Propulsive: ―Contraction ri...

Intestinal Movements and Regulation By Dr. Hira Attique Department of Physiology Overview Movements of small intestine and its regulation Ileocecal valve and ileo-cecal sphincter Movements of colon and its regulation General Principal Of GIT Functions Propulsive: ―Contraction ring ―Receptive relaxation Mixing ―Peristaltic contraction ―Local constrictive contractions Movements Of Small Intestine Movements Of Small Intestine 1. Mixing (Segmentation)contractions 2. Propulsive (Peristalsis) Contractions. 3. Migrating Motility Complex Movements Of Muscularis Mucosa Contraction Of Villi Mixing (Segmentation)Contractions Features of Segmental contraction Stimulus: ―Stretching Receptors: ―Nerve endings of enteric nervous system Response: — localized concentric contractions spaced at intervals —Fraction of a minute --> “Chop” 2-3 times per minute —Maximum frequency= 12/minute (depends on frequency of Electrical slow waves) —Duodenum and prox. Jejunum– 12/min —Ileum--> 8-9/min Integration area: ―Myenteric nerve plexus + extrinsic control Functions of Segmental Contraction Slow down transit time and increase contact time with absorption propels the chyme slowly towards the colon Mixes the chyme with digestive juices (bile, intestinal and pancreatic) Propulsive (Peristalsis) Contractions Chyme is propelled through the small intestine by peristaltic waves. Peristaltic waves: ―Occurs in any part of small intestine ―Move towards anus at a velocity of 0.5 to 2.0 cm/sec ―weak and die out after traveling only 3 to 5 centimeters. ―net movement along the small intestine -- 1 cm/min 3 to 5 hours from pylorus to ileocecal valve ― Peristaltic rush Migrating Motility Complex (MMC) Also known as “intestinal housekeeper” waves of electrical activity that sweep through the intestines in a regular cycle during fasting Trigger peristaltic waves transportation of indigestible (bone, fiber, and foreign bodies) from the stomach the small intestine past the ileocecal sphincter the colon. Appear every 1.5 hours as long as a person is fasting Migrating Motility Complex (MMC) Phase1 (quiescent period) —A long period lasting about 40 to 60 minutes with very few contractions Phase2: ―20- to 30-minute period with some peristaltic contractions Phase3: ―Shortest phase ―Rhythmically repeat for 5 to 10 minutes ―Pyloric sphincter relaxes and opens completely ―Growling noise Migrating Motility Complex (MMC) Regulation: ―Initiated by motilin in response to vagal stimulation ―migrate aborally at a rate of about 5 cm/min ―Gastric secretion, bile flow, and pancreatic secretion increase during each MMC ―Ingestion of meal suppresses it. Control of Peristalsis Neural control Hormonal control Duodenal stretch Increase motility: Gastroenteric reflex ―Gastrin, CCK, Insulin, Gastroileal reflex Motilin, Serotonin Ileocecal valve Decrease motility: Submucosal Plexus ―Secretin, Glucagon (Muscularis Mucosa and villi contraction ) Low pH Duodenum to stomach Release of gastrin GASTRIN Large Intestine Movements Movements of Colon 1. Mixing Movements (Haustrations) 2. Propulsive Movements (Mass movements ) Functions: —Absorption —Storage of fecal matter Mixing Movements (Haustrations) Large circular constrictions Contraction of circular and longitudinal muscle Unstimulated areas buldge --- Haustrations Fecal material is slowly mixed, rolled over and propelled. Propulsive Movements (Mass movements ) Slow movements occurring for many minutes 1-3times/ day Especially for about 15 min during the 1st hour after breakfast Gastrocolic and Duodenocolic Reflexes