Introduction to the Digestive System Notes

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Transcript Introduction to the Digestive System Notes

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Basic Outline
1. Movement: propels food through the
digestive system
2. Secretion: release of digestive juices in
response to a specific stimulus
3. Digestion: breakdown of food into molecular
components small enough to cross the
plasma membrane
4. Absorption: passage of the molecules
into the body's interior and their
passage throughout the body
5. Elimination: removal of undigested
food and wastes
The average male will eat about 50 tons of
food (during his lifetime!) in order to
sustain a weight of 150 lbs.
Let’s Dig In!!!!
• receptacle for food
• begins mechanical digestion through
• swallow food
A simple conduit between the mouth and
Did you know ?
It takes about 8 seconds for food to travel down
the esophagus. The average time for your
stomach to digest a high fat meal is 6 hours, as
compared 2 hours for a carbohydrate meal. The
average time for the digestion process in the
small intestine is about 3 to 5 hours. This is
followed by another 4 hours to 3 days(!) in the
large intestine.
• Short-term storage
• Substantial chemical
and enzymatic
digestion is initiated,
particularly of proteins.
• Liquefaction of food
• Slowly released into the
small intestine
Did you know ?
Your stomach produces a new lining every 3
days in order to avoid digesting itself in its
own production of acid.
Liver, Pancreas and Gallbladder
• Liver: The center of metabolic activity in the body provides bile salts to the small intestine, which are
critical for digestion and absorption of fats.
• Pancreas: provides a potent mixture of digestive
enzymes to the small intestine which are critical for
digestion of fats, carbohydrates and protein.
• Gallbladder: stores and concentrates bile, and then
releases it into the duodenum to help absorb and digest
Small Intestines
This is where the final
stages of chemical
enzymatic digestion
occur and where
almost all nutrients
are absorbed.
Large Intestine
• In all animals water is absorbed, bacterial
fermentation takes place and feces are
• Herbivores like the horse, the large
intestine is huge and of critical importance
for utilization of cellulose.
How long are your intestines?
At least 25 feet in an adult. Be glad you're
not a full-grown horse -- their coiled-up
intestines are 89 feet long!
• Rectum
It is the rectum's job to receive stool from
the colon, to let the person know that there
is stool to be evacuated, and to hold the
stool until evacuation happens.
• Anus: The anus is the last part of the
digestive tract.
Perils of Overeating
The next slide has a map of the digestive
system. Your notes need to include a map
and you’ll need to be able to label parts.
You can choose to copy figure included in
these notes or figure 38-10 on page 979 in
your textbook