The human Body (Home)
After eating a typical meal high in carbohydrates, the breakdown products (mainly glucose) are absorbed into the bloodstream via the walls of the small intestine. There is a vein, called the hepatic portal vein, which carries the glucose to the liver where one of a number of things may happen:
If the glucose levels in the blood drop below normal, such as when a person does exercise or doesn't eat for a long time, the glycogen stored in the body can be converted back to glucose, and used as a source of energy. This, however, is only a short-term energy supply, which provides glucose for body cells for only about six hours if no other supply is available. If more energy is required, the energy reserves in stored fat are tapped.
Pancreas: The pancreas has two main functions:
Gall bladder: Bile is formed by the liver. It is stored and concentrated in the gall bladder.
So, what exactly does the liver do?
The liver maintains the level of sugar, or glucose, in the blood. This glucose is a source of energy which can be used by our muscles and organs. We get this glucose from the foods we eat. If we eat too much, it is then converted to fat and stored around the body.
A person eats a meal and it is converted to glucose. The liver determines what will happen to it, according to the activity of the body and the blood sugar levels. It may get used by the liver, stored in the muscles, remain in the bloodstream, or stored as fat.
Then this person decides to go for a 10km run. What happens to their body? It requires more energy, because a lot of it is being used up during exercise. So the glycogen in the muscles is converted back to glucose, and this provides the muscles with more energy. However, this is not enough. This person is really busting a move! So, the energy stored in fat is converted back to glucose, and this is used by the muscles as energy. This is actually an example of homeostasis.
If a person eats more than they exercise, they become overweight. You could say they are putting more in than they are putting out. And if a person eats very little, but exercises a lot, they may become very skinny. They are putting more out than they are putting in.