Transcript Feeding Digestion 2 - Cal State LA

Feeding and Digestion –
Part 2
Biology 155
A. Russo-Neustadt
IV. Example of a Generalized Complete Digestive Tract:
B. 2. Salivary
glands
C. esophagus
B. Oral cavity
A. Mouth =
specialized for
food ingestion
Fig. 21.4
E. 2. liver
D. Stomach or crop
and gizzard
E. 2. Gall bladder
E. 2. pancreas
F. Large intestine
E. Small intestine
Anus
Fig. 21.5
teeth
duct from
salivary
gland
B. Oral Cavity –
1. starts mechanical breakdown of
food with chewing, uses teeth
and tongue
a. makes swallowing easier
b. increases surface area for
enzyme action
2. starts chemical breakdown of
carbohydrates
salivary
amylase
carbohydrates
smaller
carbohydrates
3. saliva moistens food bolus to
ease swallowing
Tongue with
taste buds
4. taste buds – a. stimulate
salivation, b. used in food
rejection reflex
Fig. 21.6
Oral cavity
C. Esophagus =
muscular tube that
transports food
between oral cavity
and the stomach or
crop; carries bolus
through the thoracic
cavity
esophagus
tongue
D. Stomach or a Crop and a
Gizzard
1. Stomachs and crops – serve as storage
organs, they are designed to release food
to the small intestine at the appropriate
rate for processing
2. Stomachs and gizzards – function in
mechanical breakdown of food, stomachs
make use of muscular movements, while
gizzards use grinding
D. Stomachs (con’t) –
3. Start chemical breakdown
of proteins
pepsin
Proteins
smaller proteins
HCl
4. HCl sterilizes food bolus
Fig. 21.8
E. Small Intestine
1. Continues mechanical breakdown through
muscular movements
2. Performs most chemical breakdowna. Lumen –
1. Pancreatic fluids are released into the small intestine from
the exocrine pancreas; includes bicarbonate, to
neutralize stomach acid, and enzymes
2. Bile is produced in the liver and is stored in the gall
bladder for release into the small intestine; fat emulsifier
required for the chemical digestion of fats
Reactions of the Small Intestine
Chemical bond
Lumen
glucose
small carbohydrates
glucose
pancreatic
amylase
Small proteins
proteases
Fats and oils
Amino
Amino
Amino
acid
Acid
acid
free fatty acids + monoglyceride
lipases
bile
Fig. 21.2B
The products of amylase and
protease activity cannot be
absorbed!
Only the breakdown products of lipase
action can be absorbed across the wall
of the small intestine
Fig. 21.10B
b. Intestinal epithelium has the
enzymes required to break the
final bonds in dimers and trimers
and absorb the monomers at the
same time
F. Large Intestine –
1. Water and vitamin
absorption
2. Defecation reflex
allows elimination of
non-digestible
material through the
anus
Large intestine
Fig. 21.12
anus