Download Large Intestine and Digestion Regulation

LARGE INTESTINE AND
DIGESTION REGULATION
Chapter 8
Section 8.4 -3
LARGE INTESTINE
 Only
about 1.5m long;
diameter = 2.5cm
 No
digestion occurs here
 MAIN
FUNCTION:
concentrate and eliminate
wastes (undigested chyme)
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.
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.
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.
HOW DIGESTIVE SYSTEM IS
REGULATED
The digestive system is regulated by two
different systems:
 Nervous
System
 Endocrine
System
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.
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)
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
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
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.
ENTEROGASTRONE
A
hormone secreted by the small
intestine that decreases gastric
secretions and slows peristaltic
movements.