Small Intestine
Small intestine

Small Intestine: 3 Parts, Fuctions, Enzymes, and The process of absorption

The digestive process has an important role in the body’s metabolic balance. One of the organs that role in the digestive process is the small intestine.

The small intestine takes quite a lot of space in the abdominal cavity with a length of about 6 meters and it is approximately 2.5 cm in diameter.

Parts and Functions of the small intestine

The small intestine is a part of the gastrointestinal tract located between the stomach and colon. The small intestine consists of three parts, namely duodenum (duodenal), empty intestine (jejunum), and intestinal absorption (ileum). In the duodenum, there are two lines of the pancreas and the gallbladder.


The duodenum is a part of the small intestine that is located after the stomach and connects it to the empty intestine (jejunum) with a length between 25-38 cm. The duodenum is the shortest part of the small intestine, starting from the Bulbo Duodenale and terminates in Treitz ligament.

The duodenum is responsible for channeling food to the small intestine. Histologically, there is the Brunner gland that produces mucus. The intestinal wall of the duodenum is composed of very thin layers of cells that form the mucosa muscle.

In the duodenum, the enzyme produced from the intestinal wall. Such enzymes are necessary for chemically digesting food.

Here are the small intestine functions possessed by the duodenum:

  • Helps to digest food for softer and smoother
  • Helps absorption of nutrients in food
  • Produces the necessary enzymes in the digestive system (enterokinase enzyme, maltase, lactase, Sukhrase, peptidase, lipase, Erepsin, Disachrase, Nuclelease, etc.)
  • Forming mucous muscles to aid in food digestion
  • It mucus produced by the Brunner gland
  • Helps the process of absorption of proteins, carbohydrates and substances of sugar, amino acids, fatty acids
  • As the immune system
  • As an estuary of the essential channel body

Empty intestine (jejunum)

The empty intestine (jejunum) is the second part of the small intestine that sits between the duodenum and intestinal absorption (ileum). The length of the empty intestine in older humans ranges from 1-2 meters. The empty intestine and intestinal absorption hangs on the body with the mesenterium.

The colon performs almost 90% of the nutrient absorption process from the digested food. Foods that have been broken down in the duodenum will be broken down again into smaller particles so that they are easily absorbed by the body. In the jejunum, food will undergo a chemical digestion process with the help of enzymes produced by the small intestine.

Here are the functions of the empty intestine:

  • Breakdown or cleavage of nutrients in food
  • Absorb lipophilic nutrients (protein, fat, cholesterol, and fat-soluble vitamins are vitamins A, D, E, and K)
  • Absorb water.

Intestinal absorption (ileum)

Intestinal absorption is the last part of the small intestine. In the human digestive system, intestinal absorption has a length of about 2-4 m and is located after the duodenal and Jejunum, then continued by the appendectomy. Ileum has a pH of between 7 and 8 (neutral or slightly alkaline) and serves to absorb vitamin B12 and bile salts.

In addition to absorbing food nutrients that have not been absorbed in the previous process, ileum also plays a role in regulating the Ileosekal valve in order not to occur reflux from the colon to the small intestine.

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Enzymes in The Small Intestine

In the duodenum, the enzyme produced from the intestinal wall. Such enzymes are necessary for chemically digesting food:

  • Enterokinase, to activate peptidase, i.e., that is, the activates produced by the pancreas becomes trypsin, and activates Erepsinogen into Erepsin;
  • Trypsin converts peptone into amino acids and glycerol
  • Erepsin or Dipeptidase, to convert dipeptide or peptone into amino acids;
  • Disaccharase, converts the disaccharidases into monosaccharide, namely:
    1. Maltose converts maltose into glucose + glucose
    2. Sucrose converts sucrose to fructose + glucose
    3. Lactose converts lactose into galactose + glucose
  • Lipase, converting triglycerides into glycerol and fatty acids;

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The process of absorption in the small intestine

Karmana (2007:175-176) describes the process of absorption of food in the small intestine. The space between microvilli in the colon is so small that the foodstuffs that get there are still too large to be absorbed. To overcome this, the surface of microvilli has a chemical substance called the final digestive enzyme. These enzymes break down food substances until they reach a digestible size.

The final digestive enzymes only match one type of food substance. If an enzyme comes into contact with any type of food substance that does not match, it will rapidly destroy it for easy absorption. After being broken down by the final enzyme, food substances are rapidly absorbed by the carrier proteins that are nearby. Food substances can penetrate in just one direction.

In the small intestine, there is absorption of food substances. Digestion in the colon is performed by enzymes whose functions are stimulated by a secretin hormone. The hormones that stimulate the function of the pancreas, liver, gall bladder, and the small intestinal wall is produced by the tunica mucosa duodenum or duodenum.

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Thank you very much for reading Small Intestine: Parts, Fuctions, Enzymes, and The process of absorption, hopefully useful.

Last Updated on October 1, 2021 Reviewed by Market Health Beauty Team