Describe the changes in food coming to stomach
Answers
So how does the food we eat
become the energy we need
to grow and move? The process
is complex, but it usually works
smoothly because each part of
our gastrointestinal tract that
includes the esophagus (swallowing tube), stomach, small and
large intestine, pancreas, liver and
gallbladder has a specific job it
does very well. In this article, we
will follow food as it moves
through the body and learn what happens along the way.
Our mouth starts things off by breaking up the food with our
teeth and starting the digestion of sugars with chemicals
called enzymes. Our tongue pushes the food to the back of
the mouth where it is then swallowed and travels down the
esophagus to the stomach. The esophagus does not digest
the food, but it does the important job of pushing the food
down into the stomach as well as keeping it from coming
back up into the mouth.
Once in the stomach, further digestion takes place. The
stomach produces acid that helps to kill bacteria and other
germs that may get into food. The stomach makes an
enzyme that starts digestion of protein and releases a
molecule that helps with the absorption of vitamin B12.
Once filled with food, the stomach grinds and churns the
food to break it down into small particles. It then pushes
the small particles of food into the first part of the small
intestine, called the duodenum.
The small intestine is where most of the digestion and
absorption of our food takes place. Newborn babies have
about 8 feet of small intestine at birth (250cm) and this
length grows throughout childhood to between 12 and 22
feet in adulthood (360 to 660cm), depending upon the size
of the adult. The long length of small intestine is needed so
that enough space is available for our food to be broken
down into the most elemental molecules so that it can then
be absorbed.
In the small intestine, food is processed by different
chemicals that are designed for specific components of the
meal. Proteins, fats and sugars (carbohydrates) are
digested by enzymes released by the pancreas. A tube from
the pancreas joins to the duodenum, and all the enzymes
travel together into the duodenum when food is present.
A separate tube connects the liver and gallbladder to the
duodenum. This tube allows bile, which is made by the liver
and stored in the gallbladder, to mix with food in the
intestine.
Bile is essential for complete fat digestion and for the
digestion of fat-soluble vitamins A, D, E, and K. Once the
sugars that we eat have been partially broken down by the
enzymes of the pancreas, cells lining the small intestine use
their own enzymes to fully digest the sugars.
Once proteins, fats and carbohydrates are digested,
absorption takes place in the small intestine. Most of the
digestion occurs in the first part of the small intestine while
the absorption of broken down nutrients, water, vitamins,
and minerals occurs in the rest of it. 80% of the water we
ingest is absorbed in the small intestine.
Once nutrients are absorbed by the intestine, they pass into
the blood stream and are carried to the liver. The liver has
the job of processing all the nutrients, vitamins, drugs, and
other things we ingest and absorb each day. It will turn
protein, sugar, and fat into energy which, with the help of
pancreatic hormones like insulin, will feed the cells of our
body.
The liver also gets rid of the byproducts of drugs and the
nutrients we don’t need in bile. In fact, bile is the primary
way the body gets rid of excess cholesterol and heavy
metals such as copper.
The large intestine, also called the colon, is not responsible
for digestion. Instead, its purpose is to complete water and
electrolyte (minerals found naturally in the body, such as
potassium, calcium, sodium, and magnesium) absorption
begun by the small intestine. Those components of food
that are not needed or cannot be absorbed are excreted
from the colon in stool. The color of the stool comes from
the tiny amount of bile released from the liver each day that
is not reabsorbed.
The process of turning the food we eat into the energy our
cells need is a complex and beautiful process. It requires
precise coordination between all the different organs of the
GI tract and uses hormones and nerves to allow the organs
to communicate. In fact, the GI tract has its own nervous
system with as many nerve cells as the spinal cord, allowing
us to relax and think about what we are eating without
worrying about what happens to it after we swallow!
Esophagus. When a person swallows, food pushes into the esophagus, the muscular tube that carries food and liquids from the mouth to the stomach. Once swallowing begins, it becomes involuntary and proceeds under the control of the esophagus and brain. The lower esophageal sphincter, a ringlike muscle at the junction of the esophagus and stomach, controls the passage of food and liquid between the esophagus and stomach. As food approaches the closed sphincter, the muscle relaxes and lets food pass through to the stomach.
Stomach. The stomach stores swallowed food and liquid, mixes the food and liquid with digestive juice it produces, and slowly empties its contents, called chyme, into the small intestine. The muscle of the upper part of the stomach relaxes to accept large volumes of swallowed material from the esophagus. The muscle of the lower part of the stomach mixes the food and liquid with digestive juice.
Small intestine. The muscles of the small intestine mix food with digestive juices from the pancreas, liver, and intestine and push the mixture forward to help with further digestion. The walls of the small intestine absorb the digested nutrients into the bloodstream. The blood delivers the nutrients to the rest of the body.
Large intestine. The waste products of the digestive process include undigested parts of food and older cells from the GI tract lining. Muscles push these waste products into the large intestine. The large intestine absorbs water and any remaining nutrients and changes the waste from liquid into stool. The rectum stores stool until it pushes stool out of the body during a bowel movement.