Small Intestine - Human digestive organ

Small intestine - Parts, structure, function, diseases

Small intestine is the longest part of the human digestive system. It is located in between the stomach and the large intestine (also known as colon.

The length of the small intestine

The length of the small intestine in adults is about 7 meters. It is about 2-3 cm in diameter.

Even though small intestine is longer than the large intestine, it is smaller in diameter than the large intestine. That is why it is referred to as small intestine.

Structure and Parts of small intestine

  1. Duodenum - is about 25 cm long. It is the first and the shortest part of small intestine where the food enters through a muscle called 'pyloric sphincter or pylorus' after it exits the stomach.
  2. Jejunum - is about 2.5 meters long. Most of the absorption of the nutrients takes place in jenunum.
  3. Ileum - is about 3.6 meters long. This is the longest part and the absorption of vitamin b12 takes place here. The final processing of proteins and carbohydrates also occurs in lleum. The other end of ileum opens in the large intestine and the appendix is also located there at the end.

Food moves through the small intestine due to the muscular wave like contractions. This wave like contraction is called peristalsis.

Function of small intestine

Most of the food digestion and absorption of the nutrients happen in the small intestine. The nutrients that are digested in the small intestine are proteins, lipids (fats) and carbohydrates.

Most of the chemical digestion of foods takes place here. The digestive enzymes act on foods in the small intestine. These digestive enzymes are released into the small intestine by pancreas.

The digested food, that is, the nutrients from the digested foods are then absorbed into the blood vessels. Through blood vessels, these absorbed substances are carried to different organs of the body.

Healthy small intestine is important for having a healthy digestive system as it is responsible for the absorption of nutrients. There is a lot of blood flow to it.

Small intestine diseases

There are many small intestine diseases or problems that can affect the digestive system health.

Small intestine cancer, bleeding, inflammation of small intestine, blockage or obstruction etc are some of the common problems.

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