Process of Digestion: Large Intestine

Question 1

Digestion in the large intestine

Answer 1

• mechanical
• propulsion
• limited chemical digestion
• defecetion

Question 2

Mechanical digestion and propulsion

Answer 2

• haustral contractions: mix food residue promoting water absorption
• peristalsis: slow, takes 12-24 hours for residue to pass
• mass movement: contents pushed to the rectum, triggered by distension (expansion) of the stomach or chyme in duodenum

Question 3

Chemical digestion

Answer 3

-exclusively done by bacteria (saccharolytic fermentation)
-results in buildup of gases (CO2, methane)
-produces Vit B and K
(No human enzymes secreted, just mucus)

Question 4

Absorption in large intestine

Answer 4

• absorption of water, electrolytes, and some vitamins

- only 10% of water absorption

Question 5

Defecation

Answer 5

-reflex triggered as feces pass from colon into rectum
-contractions of rectal muscles and relaxation of internal sphincter
(Caused by parasympathetic NS stimulation)
-external sphincter is voluntary
-if defecation is delayed rectal muscles relax until next muscle movement
-reflex aided by the diaphragm and abdominal muscles
-water absorption increased as feces retained

Question 6

Feces composition

Answer 6

• bacteria
• water
• inorganic salts
• indigestible material
• epithelial cells
• products of bacterial activity