Digestion - Hickman Science Department
Digestion - Hickman Science Department
The Digestive System
- or -
How Does Food Get to All My Cells???
Why the Digestive System?
• Every cell of your body needs specific
materials (like nutrients and oxygen) so
they can do the job they are made to do.
Take this lad for example. In his nose
there are cells that need nutrients.
He just can’t hold a Double
Cheese Burger up to his
nose and expect those
cells to eat!
This burger needs to be
broken down to the
molecular level before those
nose cells can use it.
And that journey from burger to molecules begins in
1. The Mouth
Digestion begins in your mouth. Your teeth
starts breaking up the food into smaller
particles while your tongue pushes the food
around making sure it gets to the teeth. This
is where mechanical digestion begins.
While the food is getting broken
down into smaller pieces it gets
mixed with saliva. This saliva
contains chemicals that start to
break the food down chemically.
Here are the salivary
glands shown in
Don’ t believe it? Try This –
1. Get an unsalted cracker (unsalted
2. Chew it up but don’t swallow it – yet
3. Let it sit in your mouth for about a
minute and describe the change in
What happens is this –
The starch in the cracker starts to be
chemically broken down by the enzymes in the
saliva. Starch is nothing more that glucose
(sugar) molecules joined together.
So, as the cracker sits in your mouth you start
to taste a sweet taste. This is also where
chemical digestion begins.
So, in review, two types of digestion begins in the
Mechanical digestion – the food is physically
broken up by the teeth and tongue.
Chemical digestion – the food is chemically
broken down by enzymes in the saliva.
2. The Esophagus
Now, the food is still a long way off in getting to
the cells in the nose. The next place the food
travels to is the esophagus. The esophagus is a
10-inch tube that carries the food to the stomach.
Before we get to far down the esophagus let’s
mention the epiglottis. It’s found at the top of
the esophagus. It’s job is to keep food out of
the lungs. Each time you swallow the
epiglottis covers the windpipe (trachea).
From a sheep
Back of tongue
When you speak the epiglottis is up. When you
swallow the epiglottis is down.
What’s this mean??
When you eat and talk you increase your
chances of choking by food going down your
What does it look like inside?
Cancer masses in the esophagus
One treatment type
for this blockage
Here is an actual
photograph of the
placed in the
3. The Stomach
Once the food gets to the
stomach the stomach uses
chemicals to try to make
the food tinier. These
chemicals are called gastric
juices and the include
hydrochloric acid and
enzymes (chemicals that
continue to break down
The food is moved around in
the stomach and mixed with
the chemicals for about 3 or 4
hours. When it is done in the
stomach, the food is now a
cream-like liquid call chyme.
But the food is still not small enough to get
into our blood stream and still must be
broken down smaller. That comes up next.
Heartburn / Ulcers
The stomach also produces mucus which lines
the stomach and prevents the acids from eating
through it. If that mucus isn’t there then ulcers
The chyme now leaves the
stomach and enters into the first
few inches of small intestine called
the duodenum. Here, chemicals
are added to the chyme from a
variety of organs:
Liver/Gall Bladder- At this point, our food is hit
with more chemicals. The liver makes a chemical
called bile which is stored in the gall bladder. Bile
breaks down the fat (from milk, butter, cheeses)
into tiny droplets. This fat will supply us with much
If the bile crystallizes it will form gall stones.
These stones may block the bile duct and
Sometimes the gall bladder has to be removed
Pancreas- The pancreas also adds a digestive
chemical as the food leaves the stomach. This
digestive juice works on breaking down the
carbohydrates (from breads, potatoes, etc.) and
the proteins (from meats, cereals, peanut butter)
4. The Small Intestine
Small Intestine - The small
intestine is a tube that is about
22 feet long. This is where the
real digestion takes place. As
the food passes through, it is
mixed with the new chemicals
and soon our "food" is now
digested small enough to be put
to use by the body.
Here is what the small
intestine looks like on
the inside. As you can
see there are many
layers to it.
Notice the little “bumps”
on the inner layer.
Those thousands of tiny bumps are called villi.
Blood vessels (capillaries) in the villi can absorb
the tiny food molecules, by diffusion, and send
them off to the rest of our body through the
Once the food gets broken down to the
molecular level and enters the bloodstream
through the villi, then the blood will take that
food all the way up to those cells in the nose (or
anywhere else in the body) and supply them
with nutrients they need.
As blood with food
capillaries the food
goes out into the
How does the food get into the cells??
Food molecules go from
an area of high
the cell) to an area of
(inside the cell).
As waste products are produced by the cell they
leave the cell in the very same way – by diffusion.
There is a higher concentration of waste product
on the inside of the cell than on the outside of the
Sometimes a person may have a
guest in their small intestine
In the Tokyo Parasite Museum – a 30 foot tapeworm
Minnow with excised tapeworm
This is why you should always give your dogs worm pills…….
Many years ago
them to help lose
5. The Large Intestine (Colon)
The large intestine, or now commonly called
the colon, is 1.5 meters in length.
The function of the colon is to simply remove
water from the waste before it leaves the
Too much water
sucked out =
Too little water sucked
out = diarrhea
Here is what the normal colon looks like on
the inside -
Cancer cells also may grow in the colon.
These growths are called polyps.
Here is a colon with polyps -
Question: How can this cancer
Answer: Nothing stops cancer
but with regular checkups you
can remove what has grown. If
not removed it can spread.
Barium enema: A series of xrays of the lower gastrointestinal
tract. A liquid that contains
barium (a silver-white metallic
compound) is put into the
rectum. The barium coats the
lower gastrointestinal tract and
x-rays are taken. This procedure
is also called a lower GI series.
Barium enema procedure. The patient lies on an
x-ray table. Barium liquid is put into the rectum
and flows through the colon. X-rays are taken to
look for abnormal areas.
Sigmoidoscopy: A procedure to
look inside the rectum and
sigmoid (lower) colon for polyps,
abnormal areas, or cancer. A
sigmoidoscope is inserted
through the rectum into the
sigmoid colon. A sigmoidoscope
is a thin, tube-like instrument
with a light and a lens for
viewing. It may also have a tool
to remove polyps or tissue
samples, which are checked
under a microscope for signs of
Colonoscopy: A procedure to
look inside the rectum and colon
for polyps, abnormal areas, or
cancer. A colonoscope is
inserted through the rectum into
the colon. A colonoscope is a
thin, tube-like instrument with a
light and a lens for viewing. It
may also have a tool to remove
polyps or tissue samples, which
are checked under a
microscope for signs of cancer.
Possible signs of colon cancer include:
• A change in bowel habits.
• Blood (either bright red or very dark) in the stool.
• Diarrhea, constipation, or feeling that the bowel does
not empty completely.
• Stools that are narrower than usual.
• Frequent gas pains, bloating, fullness, or cramps.
• Weight loss for no known reason.
• Feeling very tired.
What can be done if the growth is severe -
6. The Final Step
After the undigested mass has the water
taken from it the last step is removal from the
I think you can figure it out the rest of it from
Digestive System Animation