Digestion and Absorption

What is Digestion?

Digestion is the process of the breaking large, insoluble food molecules into smaller molecules for the purpose of absorption into the bloodstream. This process involves the use of many digestive fluids and enzymes such as saliva, mucus, bile and hydrochloric acid among others.

There are four primary stages of food digestion in the human body that includes:

  • After the intake of food through the mouth, it makes it way through the stomach into the small intestine, where it is digested.
  • The nutrients from the digested food get absorbed into the bloodstream through small pores in the small intestine.
  • The remaining undigested food is sent to the large intestine, where any unprocessed water or nutrients are reabsorbed into the body.
  • The remaining waste food product is passed out of the body as stools.

What is Absorption?

Absorption is the process of the absorbing or assimilating substances into the cells or across the tissues and organs through the process of diffusion or osmosis.

Digestion and absorption of carbohydrates

Carbohydrates are one of the basic nutrients in the human diet. There are two types of carbohydrates that can be digested by the human digestive system– sugar and starch.

Sugar is broken down in the GI tract by the small intestine and three enzymes present in the mouth namely, Lactase, Sucrase, and Maltase.

Digestion and absorption of carbohydrates

In the same way, starch is broken down with the help of the Amylase enzymes which are present in the mouth and the stomach.

After digestion, carbohydrates are absorbed in the small intestine with the help of minute finger-shaped projections known as Villi.

Digestion and Absorption of Proteins

Proteins are extremely important for the growth and replenishment of body cells and tissues.

The digestion of proteins takes place in the stomach with the help of protease and pepsin enzymes, which breaks down the proteins into amino acids. The process is facilitated by the hydrochloric acid present in the stomach.

Digestion and absorption of proteins

Amino acids are very small elements which get absorbed into the blood system through the wall of the small intestine.

Digestion and Absorption of Lipids

Lipids are organic compounds comprising of fatty acids, which are insoluble in water. Fats are the most common examples of lipids. The insoluble property of lipids makes the digestion and absorption of fats a complicated process.

Since they are hydrophobic in nature, fats stick together as a large glob of insoluble mass after reaching the stomach. It is broken down with the help of bile juice, which contains bile salts. These broken molecules are then acted upon by pancreatic lipase, the major fat-absorbing enzymes in the body.

Digestion and absorption of lipids

Pancreatic lipase breaks down fats into very small molecules of free fatty acids and monoglycerides, which are small enough for the small intestine to push through into the bloodstream.

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