Proprionic acid is almost completely removed from portal blood by the liver. Within the liver, proprionate serves as a major substrate for gluconeogenesis.
Butyric acid , most is oxidized in many tissues for energy production.
Mechanical Digestion in the Large Intestine
After a meal, a Gastroileal Reflex intensifies peristalsis in the ileum and forces any chyme into the cecum. Haustral Churning : as haustra fill and become distended, they contract and move the contents to the next haustra. Peristalsis also occurs but at a much slower rate. Mass Peristalsis : the final movement is a strong peristaltic wave beginning at the middle of the transverse colon and drives the contents into the rectum.
Chemical Digestion in the Large Intestine
This is the final stage of digestion and is activated by the activity of bacteria inhabiting the lumen. Chyme is prepared for elimination by the bacteria which ferment any remaining carbohydrates and release hydrogen, carbon dioxide, and methane gases = Flatulence Bacteria also convert the remaining proteins and decompose bilirubin.
Absorption and Feces Formation in the Large Intestine
After 3-10 hours of chyme being in the large intestine, it has become solid or semisolid because of water absorption and is now called Feces . Chemically, feces consist of water, inorganic salts, sloughed off epithelial cells, products of bacterial decomposition, unabsorbed digested materials, and indigestible parts of food. The large intestine is important part in maintaining the body’s water balance.
Defecation Reflex
Recall that Mass Peristaltic movements push fecal matter from the small colon into the rectum. Distension of the rectal wall stimulates stretch receptors which initiate the Defecation Reflex that empties the rectum. Diarrhea : is an increase in the frequency, volume and fluid content of the feces caused by increased motility and decreased absorption in the small intestine.
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