Food is moved through the laryngopharynx into the esophagus During this, the epiglottis covers entrance to trachea o 3. Involuntary Esophageal Stage 3
Food travels down the esophagus via peristalsis Peristalsis = wave like movement of contractions & relaxations that moves food down the GI tract Sphincters regulate the movement of food down the esophagus to the stomach Enterogastric Reflex o Triggered when more chyme leave the stomach o Distending stretch receptors in the duodenum o Functions: o Inhibits excessive amounts of chyme entering the duodenum o Reduces intestinal cell erosion by limiting in flow of gastric acid o Increases duration of digestion of chyme before it is moved to the small intestine o Motor impulses are sympathetic Segmentation: o Within a few hours most of stomach contents are in duodenum o Distension of stretch receptors in small intestine activates a reflex that stimulates segmentation (a mixing movement) o During segmentation, sections of the intestine are constricted o Segmentation o Increases digestion and absorption in the small intestine o No chyme movement Migrating Motility Complexes: o Peristaltic movements o Stimulated by a decrease in distension once most nutrients are absorbed o Propel undigested and liquefied chyme to the ileocecal valve Large Intestine (mechanical digestion) o Gastroileal Relfex o Ileocecal valve is normally closed so chyme can’t enter large intestine o Triggered when food enters and distends the stomach Migrating Mobility Complexes (large intestine) o Intensified by gastroileal reflex o Forcing chyme through the ileocecal valve into cecum Mechanical Digestion of Large Intestine o Local reflux causes o 1. Closure of ileocecal valve o 2. Activation of haustral churning Haustral Churning o Mixes chyme. Helps absorption of water, salts and vitamins o Propels contents of colon along the large intestine 4
Defecation (pooping) o Activated by stretch receptors stimulated by filling of the rectum o ANS reflex which sensory impulses are sent to the control center in spinal cord o Parasympathetic impulses travel down spinal sacral nerves o Stimulate longitudinal contractions of r ectum forcing feces through butt hole o Relax internal anal sphincter allow poop to move to the external anal sphincter o Voluntary relaxation of external anal sphincter allows defecation to be completed Describe the function of pancreatic juice . Contain enzymes that complete digestion of starch called pancreatic amylase Pancreatic enzymes that complete the digestion of protein called trypsin, chymotrypsin, carboxypeptidase Alkaline High concentration of bicarbonate ions – makes it useful in neutralizing acidic gastric acid E nzymes that pass to the small intestine where they help break down carbs, proteins and fats in chyme Juice secretion is regulated by the hormones secretin and cholecystokinin.
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