So there you are, sitting at lunch, enjoying some grilled
chicken pizza and a few orange wedges. When you're finished,
you take a last drink of milk, wipe your mouth, and head to your
next class. In a few minutes you're thinking about the capital
of Oregon or your science fair project. You've completely
forgotten about that pizza lunch you just ate. But it's still
in your stomach - sort of like a science experiment that happens
all the time!
Your
digestive
(say: dye-
jes
-tiv)
system
started working even before you took the first bite of your pizza.
And the digestive system will be busy at work on your chewed-up
lunch for the next few hours - or sometimes days - depending upon
what you've eaten. This process, called digestion, allows your
body to get the nutrients and energy it needs from the food you
eat. So let's find out what's happening to that pizza,
orange, and milk.
The Mouth Starts Everything Moving
Even before you eat, when you smell a tasty food, see it, or
think about it, digestion begins.
Saliva
(say: suh-
lye
-vuh), or spit, begins to form in your mouth. When you do eat, the
saliva breaks down the chemicals in the food a bit, which helps
make the food mushy and easy to swallow. Your
tongue
helps out, pushing the food around while you chew with your teeth.
When you're ready to swallow, the tongue pushes a tiny bit of
mushed-up food called a
bolus
(say:
bow
-lus) toward the back of your throat and into the opening of your
esophagus, the second part of the digestive tract.
The
esophagus
(say: ih-
sah
-fuh-gus) is like a stretchy pipe that's about 10 inches (25
centimeters) long. It moves food from the back of your throat to
your stomach. But also at the back of your throat is your windpipe,
which allows air to come in and out of your body. When you swallow
a small ball of mushed-up food or liquids, a special flap called
the
epiglottis
(say: eh-pih-
glah
-tiss) flops down over the opening of your windpipe to make sure
the food enters the esophagus and not the windpipe.
If you've ever drunk something too fast, started to cough,
and heard someone say that your drink "went down the wrong
way," the person meant that it went down your windpipe by
mistake. This happens when the epiglottis doesn't have enough
time to flop down, and you cough involuntarily (without thinking
about it) to clear your windpipe.
Once food has entered the esophagus, it doesn't just drop
right into your stomach. Instead, muscles in the walls of the
esophagus move in a wavy way to slowly squeeze the food through the
esophagus. This takes about 2 or 3 seconds.
See You in the Stomach
Your stomach is attached to the end of the esophagus. It's a
stretchy sack shaped like the letter J. It has three important
jobs:
- to store the food you've eaten
- to break down the food into a liquidy mixture
- to slowly empty that liquidy mixture into the small
intestine
The stomach is like a mixer, churning and mashing together all
the small balls of food that came down the esophagus into smaller
and smaller pieces. It does this with help from the strong muscles
in the walls of the stomach and
gastric
(say:
gas
-trik)
juices
that also come from the stomach's walls. In addition to
breaking down food, gastric juices also help kill bacteria that
might be in the eaten food.
Onward to the small intestine!
22 Feet Isn't Small at All
The
small intestine
(say: in-
tes
-tin) is a long tube that's about 1 1/2 inches to 2 inches
(about 3.5 to 5 centimeters) around, and it's packed inside you
beneath your stomach. If you stretched out an adult's small
intestine, it would be about 22 feet long (6.7 meters) - that's
like 22 notebooks lined up end to end, all in a row!
The small intestine breaks down the food mixture even more so
your body can absorb all the vitamins, minerals,
proteins
,
carbohydrates
, and
fats
. The chicken on your pizza is full of proteins - and a little fat
- and the small intestine can help extract them - with a little
help from three friends: the
pancreas
(say:
pan
-kree-us),
liver
, and
gallbladder
.
Those organs send different juices to the first part of the
small intestine. These juices help to digest food and allow the
body to absorb nutrients. The pancreas makes juices that help the
body digest fats and protein. A juice from the liver called
bile
helps to absorb fats into the bloodstream. And the gallbladder
serves as a warehouse for bile, storing it until the body needs
it.
Your food may spend as long as 4 hours in the small intestine
and will become a very thin, watery mixture. It's time well
spent because, at the end of the journey, the nutrients from your
pizza, orange, and milk can pass from the intestine into the blood.
Once in the blood, your body is closer to benefiting from the
complex carbohydrates in the pizza crust, the vitamin C in your
orange, the protein in the chicken, and the calcium in your
milk.
Next stop for these nutrients: the liver! And the leftover waste
- remnants of the food that your body can't use - goes on to
the large intestine.
Love Your Liver
The nutrient-rich blood comes directly to the liver for
processing. The liver filters out harmful substances or wastes,
turning some of the waste into more bile. The liver even helps
figure out how
many
nutrients will go to the rest of the body, and how many will stay
behind in storage. For example, the liver stores certain vitamins
and a type of sugar your body uses for energy.
That's One Large Intestine
At 3 or 4 inches around (about 7 to 10 centimeters), the
large intestine
is fatter than the small intestine and it's almost the last
stop on the digestive tract. Like the small intestine, it is packed
into the body, and would measure 5 feet (about 1.5 meters) long if
you spread it out.
The large intestine has a tiny tube with a closed end coming off
it called the
appendix
(say: uh-
pen
-dix). It's part of the digestive tract, but it doesn't
seem to do anything, though it can cause big problems, because it
sometimes gets infected and needs to be removed.
Like we mentioned, after most of the nutrients are removed from
the food mixture, there is waste left over - stuff your body
can't use. This stuff needs to be passed out of the body. Can
you guess where it ends up? Well, here's a hint: It goes out
with a flush.
Before it goes, it passes through the part of the large
intestine called the
colon
(say:
coh
-lun), which is where the body gets its last chance to absorb the
water and some minerals into the blood. As the water leaves the
waste product, what's left gets harder and harder as it keeps
moving along, until it becomes a solid. Yep, it's poop (also
called stool or a bowel movement).
The large intestine pushes the poop into the
rectum
(say:
rek
-tum), the very last stop on the digestive tract. The solid waste
stays here until you are ready to go to the bathroom. When you go
to the bathroom, you are getting rid of this solid waste by pushing
it through the
anus
(say:
ay
-nus). There's the flush we were talking about!
Dig That Digestive System
You can help your digestive system by drinking water and eating
a healthy diet that includes foods rich in fiber. High-fiber foods,
like fruits, vegetables, and whole grains, make it easier for poop
to pass through your system. The digestive system is a pretty
important part of your body. Without it, you couldn't get the
nutrients you need to grow properly and stay healthy. And next time
you sit down to lunch, you'll know where your food goes - from
start to finish!
Reviewed by:
Steven Dowshen, MD
Date reviewed: March 2007
Note: All information is for educational purposes only. For specific medical advice,
diagnoses, and treatment, consult your doctor.
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