small intestine

  • The small intestine is the location of most digestion and nutrient absorption

  • It is about 10 feet long in an adult

  • The small intestine has three sections:

    • duodenum

    • Jejunum

    • ilium

  • After the ileum, it joins the large intestine at the ileocecal sphincter

  • To absorb nutrients efficiently, the small intestine is lined with villi and microvilli

    • Villi- tiny, fingerlike projections, in the lining of the intestine filled with blood vessels

processes in the small intestine

  • Many glands line the small intestine and secrete digestive hormones

    • Alkaline mucus from mucosas glands and duodenal glands – protects from pathogens

    • Secretin – inhibits the release of gastric juices when chyme is very acidic

    • Cholecystokinin (CCK) – causes the gallbladder to release bile

    • Intestinal juice

      • maltase, sucrase, lactase – break down sugars

      • Peptidase, and enterokinase – break down proteins

  • Because the small intestine needs time to absorb nutrients, the chyme must be slowed down

  • Circular muscles in the intestinal wall, cause segmentation of the chyme

    • This is in contrast to peristaltic contractions, which involve longitudinal muscles