Lecture 22 Flashcards
Large intestine: Smooth muscle =
mechanical digestion
Mechanical: Peristaltic waves:
haustral churning
gastroilial reflex
gastrocolic reflex
haustral churning-
relaxed pouches are filled from below by muscular contractions
gastroilial reflex =
when stomach is full, gastrin hormone relaxes ileocecal sphincter so small intestine will empty and make room
gastrocolic reflex =
when stomach fills, a strong peristaltic wave moves contents of transverse colon into rectum
Chemical Digestion in Large Intestine:
- No enzymes are secreted only mucous
- Bacteria ferment
- Bacteria produce vitamin K and B in colon
Bacteria ferment: 1st step
- undigested carbohydrates into carbon dioxide & methane gas
Bacteria ferment: 2nd step
- undigested proteins into simpler substances (indoles)—-odor
Bacteria ferment: 3rd step
- turn bilirubin into simpler substances that produce color
Absorption in the Large Intestine:
- Some electrolytes—Na+ and Cl-
2. After 3 to 10 hours, 90% of H2O has been removed from chyme
Feces are
semisolid by time reaches transverse colon
Feces =
dead epithelial cells, undigested food such as cellulose, bacteria
Defecation: What moves feces into the rectum?
Gastrocolic reflex
Defecation: What signals the sacral spinal cord?
stretch receptors
Defecation: What contracts muscles of the rectum and relax the internal anal sphincter?
parasympathetic nerves
Defecation: What is voluntarily controlled?
external sphincter
Diarrhea =
chyme passes too quickly through intestine
H2O not absorbed
Constipation–
decreased intestinal motility
too much water reabsorbed
Dietary fiber- Insoluble fiber:
- woody parts of plants
- speeds up transit time & reduces colon cancer
Dietary fiber- Soluble fiber:
- gel-like consistency = beans, oats, citrus white parts, apples
- lowers blood cholesterol
How does soluble fiber lower blood cholesterol?
by preventing reabsorption of bile salts so liver has to use cholesterol to make more
Functions of food:
source of energy
essential nutrients
stored for future use