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to move inward as the inspiratory movements drop the diaphragm. These contractions elevate abdominal pressure, which squeezes the stomach and raises its pressure. Once the lower esophageal sphincter opens, the stomach contents enter the esophagus. Further strong contractions will push the stomach contents through the upper esophageal sphincter and eject them through the mouth. The intestino-intestinal reflex inhibits the contraction of the small intestine when it has been severely distended. The ileogastric reflex responds to a distention of the ileum by inhibiting gastric motility. The gastroileal reflex responds to the presence of chyme in the stomach by increasing motility of the ileum. The colonocolonic reflex responds to distention in one region of the colon by relaxing the other regions. The gastrocolic reflex responds to food in the stomach by increasing colonic motility and frequency of mass movement.The defecation reflex is triggered by distention of the rectum. This stimulates contraction of rectal smooth muscle cells. At the same time, peristaltic contractions are initiated in the sigmoid colon. Ultimately, the internal anal sphincter relaxes while the external sphincter contracts. This muscle can be relaxed voluntarily. Diff: 8 Page Ref: 59620.5 Short Answer Questions1) Which structures of the gastrointestinal tract have a wall structure that differs from most of thetract?2) What are the three layers of the mucosa, from innermost to outermost?3) Where are Peyer's patches?
4) The ________ is the portion of the enteric nervous system located within the muscularis mucosa.Answer: myenteric (Auerbach's) plexusDiff: 4 Page Ref: 5735) The G cells that line the lumen of the stomach are responsible for the secretion of ________.Answer: gastrinDiff: 4 Page Ref: 5756) The stomach's lining is protected from the acidic contents of the lumen by a layer of mucus and bicarbonate called ________.Answer: gastric mucosal barrierDiff: 4 Page Ref: 5757) What are the two sources of bicarbonate secreted into the lumen of the small intestine?Answer: exocrine pancreas and secretory cells in the crypts of LieberkuhnDiff: 5 Page Ref: 5758) Microvilli of epithelial cells in the small intestine make up the ________.Answer: brush borderDiff: 5 Page Ref: 5769) What blood vessel supplies the liver with oxygenated blood?10) What segments of the colon are specialized for absorbing water and ions?11) ________ is the process whereby fecal material is removed from the body.Answer: DefecationDiff: 3 Page Ref: 57812) The endocrine portion of the pancreas is composed of ________.