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I. Functions of the Digestive
System
A. Functions-
1. Digestion:
The process by which
your body Breaks down
food into small nutrient
molecules.
(mechanical and chemical)
2. Absorption:
The process by which nutrient molecules
pass through the wall of your digestive
system into your blood.
3. Elimination:
Materials that
are not absorbed
are eliminated
from the body
as waste (ie.
Fiber)
II. Types of Digestion:
Mechanical – foods are physically
broken down into smaller pieces
B. Chemical – chemicals produced by the
body break foods into smaller chemical
building blocks
C. Both begin in the mouth.
A.
III. The Process of Digestion
A. The Mouth
1.
Mechanical Digestion
a. Teeth cut food into bite-size pieces, then crush
and grind them into smaller pieces.
b. Saliva mixes with and moistens the food as you
chew to aid you in swallowing.
2. Chemical Digestion
a. Saliva contains chemicals called enzymes
which are proteins that speed up chemical
reactions in the body.
b. The enzymes break down starches into sugar
molecules.
B. Esophagus
1. A muscular tube that connects the mouth to the
stomach.
a.
2.
It’s lined with mucus, which allows food to move easily
through the esophagus.
At the top of the esophagus, there is a flap of
tissue called the epiglottis. It covers the opening
to your trachea (windpipe) when you swallow so
that you don’t choke on your food.
a.
b.
Food remains in the esophagus for about 10 seconds.
After food enters the esophagus, contractions of smooth
muscles push the food toward the stomach. (Peristalsis)
C. Stomach
1.
2.
A J-shaped, muscular pouch located in the abdomen.
Most mechanical digestion and some chemical digestion
a. Mechanical – Three strong layers of smooth
muscle surround the stomach and contract to
churn the food. This mixes it with fluids that further
the digestion process.
b. Chemical – The churning of mechanical digestion
mixes the food with strong enzymes that continue
to break down food.
3.
4.
Hydrochloric acid (HCl) in your stomach, provides the
ideal environment for the enzymes for proteins to work.
Food remains in the stomach for about three hours.
When it is a thick liquid, it is ready to move to the next
section of the digestive system.
D.
Small Intestine
1.
The part of the digestive system where the
most chemical digestion and absorption of
nutrients takes place.
The digestion of fats takes place here.
Several secretions get added here from
other organs. (Liver and Pancreas)
The small intestine is lined with millions of
tiny projections (villi) that help increase the
surface area for the absorption of nutrients
from your food.
2.
3.
4.
E.
1.
2.
3.
Liver
The role of the liver in the digestive system
is to produce bile
Bile is a substance that breaks up fat
particles. It is not an enzyme, but it does
break up large fat molecules into small fat
droplets which can be broken down easier.
Bile is stored and concentrated in the
gallbladder.
F.
1.
2.
Pancreas
The pancreas produces enzymes that flow
into the small intestine and help break down
starches, proteins, and fats.
It also produces insulin which regulates the
amount of sugar in your blood.
6.
7.
8.
9.
The small intestine is where fat digestion takes
place, however all nutrients are digested in the
small intestine.
The tiny projections inside of the small intestine
are called villi. Villi increase the surface area to
absorb more nutrients.
Bile is a chemical made by the liver that breaks
down fat molecules into smaller fat molecules.
Bile is stored and concentrated in the
gallbladder.
G.
Large Intestine
1.
The large intestine is the last section of the
digestive system.
The large intestine contains bacteria that feed on
materials as they pass through. Many of them
make vitamins like vitamin K.
Water is absorbed from the digested food
materials into the bloodstream.
The large intestine ends in a tube called the
rectum, which is where wastes are compressed
into solid form.
2.
3.
4.