The
Digestive
Process
Caution: some pictures used in this
presentation are actual photos of the
human body.
Functions of the Digestive System
• The digestive system has three main
functions:
– 1. Breaks down food into molecules the
body can use.
– 2. These molecules are absorbed into the
blood and carried throughout the body.
– 3. Wastes are eliminated from the body.
The Mouth
Mechanical and Chemical Digestion
• Mechanical: Teeth tear and slash the food
into smaller pieces.
• Chemical: Enzymes “change” the pieces of
food into nutrients your body can use.
– Example: starch (like crackers) are changed into
sugar molecules that fuel your body.
epiglottis
There is a flap of
tissue called the
epiglottis that seals
off your windpipe,
preventing food
from entering your
lungs.
The Esophagus
There are two tubes
that divide off your
throat. One opening
leads to your
windpipe and one
leads to your
stomach.
The one that carries
food to your
stomach is the
esophagus.
• The esophagus is a muscular tube that
connects the mouth to the stomach. It is lined
with mucus, which is a thick, slippery
substance produced by the body.
• It takes food about 10 seconds to travel down
to the stomach.
• The smooth muscles that line the esophagus
move the food with contractions called
peristalsis.
The Stomach
The stomach is a J-shaped, muscular pouch.
This organ uses both mechanical and chemical
digestion to break down food.
– Mechanical: three strong layers of smooth muscle
contract to produce a churning motion. This action
mixes the food with fluids.
– Chemical: as the churning food makes contact with
the digestive juice pepsin, which is made in the cells
that line the stomach, some foods are broken down
into smaller, different molecules. Digestive juice also
contains hydrochloric acids . This creates an excellent
environment for the pepsin to work in. The acid also
kills many bacteria found in food.
Food remains in the stomach until all the solid
material has been broken down into liquid
form.
Homework
• Read pages 516-521. Add to your notes when
necessary.
• Complete the Math Analyzing Data on the top
of page 520. Answer the questions in
complete sentences.
• Review all key terms for this section.
Last Night’s Homework
• Answers:
– 1. The values on the y-axis represent the
percentage of egg white digested.
– 2. I estimate that after about 14 hours half of the
protein was digested.
– 3. After 16 hours of digestion about 70% was
completed.
– 4. During the 12-16th hours is when most of the
digestion occurred.
Pop Quiz
•
Take a piece of loose leaf and put your heading on it and number 1-5.
•
Write the body part for each description below.
– 1. this is a J-shaped muscular organ where
both mechanical and chemical digestion occur.
– 2. This is the area where your incisors are
located.
– 3. Peristalsis first occurs in this mucus lined
tube.
– 4. This flap of tissue seals off your windpipe
when you swallow food.
– 5. These body parts provide the first stage of
mechanical digestion.
Answers to Pop Quiz
•
•
•
•
•
1.
2.
3.
4.
5.
Stomach
Mouth
Esophagus
Epiglottis
Teeth
The Small Intestine
• This is where the most all chemical digestion
takes place.
• 6 meters in length
• 2-3 centimeters wide
• Almost all nutrients are absorbed by the villi
that line the inside of the small intestine. The
nutrients are then into blood vessels, where
the nutrients are carried to all parts of the
body.
The Liver
• The liver has several jobs in several body systems.
• In digestion its job is to make bile.
• Bile is a substance that breaks up fat particles.
– Bile flows from the liver into the gallbladder, the organ
that stores bile.
– Bile is not an enzyme. It DOES NOT chemically digest
foods. It mechanically does by physically breaking
large fat particles into smaller fat droplets. These
droplets can now be chemically broken down by
enzymes produced in the pancreas.
The Gallbladder
Pancreas
• A triangular shaped
organ that lies between
the stomach and the
first part of the small
intestine.
• It too has many
responsibilities in many
systems.
• In digestion it produces
enzymes that flow into
the small intestine and
help break down
starches, proteins, and
fats.
Large Intestine
• Nearly all nutrients have been absorbed as the
material now reaches the large intestine.
• 1.5 meters long and 5 cm in diameter
• U-shaped
• Filled with “good” bacteria that makes a few
vitamins, like vitamin K, for your body.
• As the remaining material moves through the
large intestine, water is absorbed into the
bloodstream. The remaining material is
readied for elimination from the body.
Homework
•
•
•
•
Read pages 524-527
Add to notes when necessary.
Review for test (Nov 23)
Tomorrow is a lab, you do NOT need your text
book. All you need to bring is your notebook
and something to write with.