In the previous lessons we discussed the absorption of food molecules into the blood (click here). In this lesson we will learn about the last stage of the digestive system, assimilation.
What is assimilation?
Assimilation is the process of converting the absorbed food particles into new protoplasm or using it to provide energy to the body for different vital activities.
The process of assimilation is mainly carried out in the liver. The blood vessels carrying the nutrients unite to form a bigger vein, hepatic portal vein, which transports nutrients from the small intestine to the liver.
Absorbed substances that go to the liver are:
Glucose
Amino Acids
Fats
Glucose:
Glucose is used by all the cells as a source of energy. It is first oxidized during cellular respiration, to release energy to perform the vital activities of the cells. Blood containing glucose pass through the liver, where excess glucose is stored as glycogen, by a hormone insulin (check out our notes on the digestive system and the organs associated with it.) When the body needs energy, the stored glycogen is converted back to glucose, by a hormone glucagon. Then the glucose is transported around the body.
Amino Acids:
Amino acids which enter the cells are used to make new protoplasm for growth and repair of worn out parts. However, excess amino acids is stored in the liver in the form of urea, by the process of deamination. Deamination is the process of removing amino groups (NH2) from amino acids and are converted to urea. Urea is removed from the body through urine. The deaminated amino acids are brought to liver where they are converted to glucose and stored as glycogen.
Fats:
Fats are good source of energy and are carried by lymphatic capillaries. These capillaries join together to form larger lymphatic vessels which discharge fats into the bloodstreams. Blood carries fats to all parts of the body, especially liver. Here it is converted to such forms, that it can be used or stored. Fats is not required in a large amount by the body in the presence of glucose, however when there is less amount of glucose, like during fasting, fats are transported to all body cells to provide energy for vital activities. Fats are used in protoplasm especially in cell membranes. Fats are stored in special tissues called adipose tissues. These tissues are found around the heart and kidneys and under the skin. They protect the organs and acts as shock absorbers.
To check all the previous notes on "Digestive System", go through the following:
Lesson #1 : Click Here
Lesson #2: Click Here
Lesson #3: Click Here
Lesson #4: Click Here
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