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The main part of the digestive system is the
digestive tract. This is like a long tube, some nine metres in total, through the middle of the body. It starts at the mouth,
where food and drink enter the body, and finishes at the anus, where leftover food and wastes leave the body
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Mouth
Teeth bite off and chew food into a soft pulp that is easy to swallow. Chewing mixes the food
with watery saliva, from 6 salivary glands around the mouth and face, to make it moist and slippery.
Oesophagus
The oesophageus, or gullet, is a muscular tube. It takes food from the throat and pushes it
down through the neck, and into the stomach. It moves food by waves of muscle contraction called peristalsis. |
Stomach
The stomach has thick muscles in its wal. These contract to mash the food into a sloppy soup.
Also the stomach lining produces strong digestive juices. These attack the food in a chemical way, breaking down and dissolving
its nutrients.
Pancreas
The pancreas, like the stomach,
makes powerful digestive juices called enzymes which help to digest food further as it enters the small intestines.
Gall Bladder
This small baglike part is tucked under the liver. It stores a fluid called bile,
which is made in the liver. As food from a meal arrives in the small intestine, bile flows from the gall bladder along the
bile duct into the intestine. It helps to digest fatty foods and also contains wastes for removal.
Small Intestines
This part of the tract is narrow, but very long - about 20 feet. Here, more enzymes
continue the chemical attack on the food. Finally the nutrients are small enough to pass through the lining of the small intestine,
and into the blood. They are carried away to the liver and other body parts to be processed, stored and distributed.
Liver
Blood from the intestines flows to the liver, carrying nutrients, vitamins and minerals, and
other products from digestion. The liver is like a food-processing factory with more than 200 different jobs. It stores some
nutrients, changes them from one form to another, and releases them into the blood acccording to the activities and needs
of the body.
Large Intestine
Any useful substances in the leftovers, such as spare water and body minerals,
are absorbed through the walls of the large intestine, back into the blood. The remains are formed into brown, semi-solid
faeces, ready to be removed from the body.
Rectum and Anus
The end of the large intestine and the next part of the tract, the rectum,
store the faeces. These are finally squeezed through a ring of muscle, the anus, and out of the body.
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