金点晨会报告【财经要闻及点评】20.pptVIP

Peristalsis Distinctive pattern of smooth muscle contractions that propels foodstuffs distally through the esophagus and intestines Mediated by…. Local, intrinsic nervous system Ex: peristalsis is not affect to any significant degree by vagotomy or sympathectomy Peristalsis Peristalsis – law of intestine Bolus of food →Mechanical distension and mucosal irritation → stimulates afferent enteric neurons → 2 effects Excitatory motor neurons above the bolus activated → contraction of smooth muscle above the bolus Via Ach, substance P Ileocecal Valve What it is Opening to large intestines Function: (1) prevent the repulsion (2) control the emptying normally closed. Short-range peristalsis in terminal ileum and distension relaxes IC sphincter -- small amount of chyme is squirted into the cecum. Distension of cecum contracts IC sphincter. Gastro-ileal reflex: enhances ileal emptying after eating. The hormone gastrin relaxes ileocecal sphincter. MMC(migrating motor complex) PhaseⅠ: Almost have no contractions 40-60 min PhaseⅡ: have contractions, only have few 30-45 min PhaseⅢ: have continuous contractions 5-10 min Large intestine Functions Absorption of water and electrolytes Storage of feces In non-ruminant herbivores, fermentative digestion and absorption of nutrients Motility patterns mixing (form haustrations) propulsive (mass movements) Segmentation in large intestine Haustration: （结肠袋）modified form of segmentation in which intense, local contraction of circular muscle causes large intestine to appear to bulge into sacs Mass movement Occurs in colon; also known to occur in equine cecum Period of intense propulsive activity that moves entire contents of colon distally toward rectum Contractions progress for long distance such that long length of colon contracts as a unit Entry of fecal matter into recturn triggers defecation reflex Mass Movement * * IV MOTILITY OF THE SMALL INTESTINE Function of Intestinal Motility To mix chyme with digestive secretion To bring fresh