Transcript Digestion Lecture #2

DIGESTIVE SYSTEM
15.2
I. STEPS OF DIGESTION
A. Ingestion (eat food)
B. Digestion (break food down
into small pieces that can
be moved into the blood)
C. Absorption (nutrients
diffuse into bloodstream)
D. Elimination (remove wastes)
II. TYPES OF DIGESTION
A. Mechanical- Food is mixed,
chewed or churned
B. Chemical- Chemical reactions
occur that break down food into
smaller pieces
1. Enzymes- special
proteins that break down
food
III. DIGESTIVE ORGANS
A. Mouth
1. Mech: Teeth chew,
tongue moves food, swallow
2. Chem: Saliva contains an
enzyme called amylase that
breaks down starches
into simple sugars
III. DIGESTIVE ORGANS
B. Esophagus
1. Epiglottis covers the
trachea when swallowing.
2. Peristalsis- Involuntary
muscle contractions that
move food down the
esophagus
III. DIGESTIVE ORGANS
C. Stomach
1. Mech: Food is mixed by
stomach contractions
(peristalsis)
2. Chem: Food is mixed with
an enzyme called pepsin
to break down proteins
III. DIGESTIVE ORGANS
a. HCl activates the pepsin
b.Stomach is protected
from the acid by mucus
3. The food is turned into
chyme in 2-4 hours.
III. DIGESTIVE ORGANS
D. Small (diameter) Intestine
1. Duodenum- First section of
the S.I. where most digestion
takes place
a. Fats are broken down by
a green fluid called bile
b. Enzymes from the
pancrease break down
carbs, protein and fats
III. DIGESTIVE ORGANS
2. Absorption of nutrients
takes place in the rest of
the S.I.
a. Villi- Fingerlike
projections of the S.I. that
increase surface area and
enhance absorption.
b. Towel demonstration
III. DIGESTIVE ORGANS
c. Nutrients are absorbed
in the S.I. and enter the
bloodstream so they can be
used by cells.
III. DIGESTIVE ORGANS
E. Large (diameter) Intestine
1. Any remaining chyme
enters the L.I. where water
is absorbed back into the
body
a. Feces is formed and
stored in the rectum
III. DIGESTIVE ORGANS
2. The feces is excreted
through the anus.
a. Feces may be stored
for up to 3 days!
The entire digestion process
takes 24-35 hours!
IV. ACCESSORY ORGANS
A. Liver- Secretes bile into
the S.I. to break down fats
1. Bile is stored in the
gallbladder until needed.
IV. ACCESSORY ORGANS
B. Pancreas- Secretes enzymes
into S.I. to breakdown fats,
carbs and proteins.
1. Also makes insulin that
helps glucose (sugar) pass
from the bloodstream into
cells.
V. BACTERIA
A. Not all bacteria are bad!
1. They make vitamins in the
L.I.
2. They break down
undigested compounds
a. Gas is a by product!
1.
2.
3.
4.
RECAP
What are the 4 steps in the
digestive process?
What are the main digestive
organs?
What are the accessory
organs?
Why are enzymes important?