Digestive 4

• Chemical Digestion in the Colon


  1. Substances are further broken down by bacteria

  2. Any remaining substances are fermented and release gas

  3. Some vitamins are synthesized by bacterial action
• Flatulence


  When carbs are fermented and there is an excessive amount of gas
• Absorption and Feces Formation


  1. Colon absorbs water, electrolytes, and some vitamins as chyme remains for 3-10hrs

  2. Feces consist of water, inorganic salts, sloughed-off epithelial cells, bacteria, products of bacterial decomposition, and undigested portions of food
• Defecation Reflex


  1. Rectal wall distends and stretch receptors send sensory nerve impulses to the sacral spinal cord

  2. Motor impulses travel back to the descending colon, sigmoid colon, rectum, and anus

  3. Longitudinal rectal muscles, abdominal muscles, and the diaphragm contract and the internal anal sphincter opens
• Normal bowel movements


  Range between 2-3 per day or as minimal as 3-4 per week
• Mechanical Digestion: Defecation Reflex


  1. Interactions Animation: Mechanical Digestion in the Large Intestine

  2. Defecation: Animation section 4
• Phases of Digestion


  1. Cephalic phase: Smell, sight, thought, and taste of food stimulates gastric secretion and motility

  2. Gastric phase: Neural and hormonal mechanisms promote secretion and motility

  3. Intestinal phase: Neural and hormonal mechanisms occur once food enters the small intestine
• Hormonal Control of Digestion

  Interactions Animation: Hormonal Control of Digestive Activities