1. Large Intestine and Digestion Regulation
Chapter 8
Section

2. LARGE INTESTINE Only about 1.5m long; diameter = 2.5cm
No digestion occurs here
MAIN FUNCTION: concentrate and eliminate wastes (undigested chyme)

3. ANAEROBIC INTESTINAL BACTERIA
The large intestine houses bacteria such as E. coli.
The bacteria break down water and salts absorbed from remaining chyme
They also produce vitamins B-12 and K and some amino acids.

4. FECES Any remaining indigestible material + colon bacteria.
Pass into rectum and anal canal (last 20cm of large intestine).
After, exit body through anus
Rectum is responsible for storing feces until they are excreted.

5. Anus Controlled by 2 sphincters One set we have control of.
Other set controlled by nervous system.
When rectum full = nerves trigger reflex that moves feces out of body via PERISTALSIS.

6. HOW DIGESTIVE SYSTEM IS REGULATED
The digestive system is regulated by two different systems:
Nervous System
Endocrine System

7. NERVOUS SYSTEM
Seeing, smelling or tasting food will produce gastric juice even before there is any food in the stomach.
Swallowing motions also stimulate the production of gastric juices, regardless of whether food is actually swallowed.

8. Hormones secreted for digestive control include: Gastrin
EDOCRINE SYSTEM
The endocrine system is responsible for producing and secreting hormones for many different things in our body.
Hormones secreted for digestive control include:
Gastrin
Secretin
CCK (cholecystokinin)
Entergastrone

9. Stimulated by: proteins in food that just arrived in stomach.
Gastrin
Stimulated by: proteins in food that just arrived in stomach.
Stimulates: HCl and an inactive form of pepsin to be secreted.
Inhibited by: low pH in stomach caused by secretion of HCl.
Negative Feedback

10. Hormones secreted by the duodenum. Secrete into bloodstream.
SECRETIN and CCK
Hormones secreted by the duodenum.
Secrete into bloodstream.
Inhibit stomach contractions and secretions
BECAUSE: when duodenum is already occupied with some chyme, no more chyme can enter until the PREVIOUS AMOUNT can be processed

11. OTHER REGULATORY FUNCTIONS
CCK stimulates increase in digestive enzyme secretions from pancreas and contractions of gall bladder
More bile into duodenum = more emulsification of fats.
SECRETIN stimulates release of bicarbonate from pancreas.

12. ENTEROGASTRONE
A hormone secreted by the small intestine that decreases gastric secretions and slows peristaltic movements.