Anatomy of Small intestine |PARTS |FUNCTION| STURUCTURE

Introduction:

Nutrition not only involves the macro nutrients and micro nutrients, it also involves their digestion that how they get into our body or becomes part of human muscle mass. Macro nutrients include carbohydrates, proteins and fats. After being digester, they are absorber into the human body through different routes. There are different sites for the digestion of macro nutrients. For example, main site for protein digestion is stomach and for that of lipids it is the small intestine.  But this article will focus only on the anatomy and absorption in small intestine. If you want to know more about digestion then read our article Basic Digestion and click on this link:

Anatomy of small intestine:

Small intestine is larger than large intestine in size. It is exist between stomach and large intestine in peritoneal cavity. There are three basic parts of small intestine. This phase of article will only focus on anatomy and function of small intestine and its parts are describe below. So, basic three types of small intestine are given below:

1. Duodenum
2. Jejunum
3. Ileum

There are two sphincters also involve:

1. Pyloric sphincter
2. Ileocecal valve

Duodenum:

It is starting part of small intestine. It starts from pyloric sphincter and open in jejunum. Duodenums about 25-38 cm long. It is present in upper abdomen. Duodenum has C-shaped structure.

Duodenum is further divide into two parts:

1. Peritoneal
2. Retroperitoneal

Jejunum:

jejunum is second portion of small intestine. It exists between duodenum and ileum. It is about 2.5 m long. jejunum is the most important part of small intestine because absorption and digestion occurs in this part. jejunum has villi and large surface area that is involve in absorption.

Ileum:

It is the last section of small intestine. It has also villi and involved in the digestion and absorption of fats. Bile acid comes in this part. Bile acid is pancreatic secretion that involve in the emulsification of fat. It joins at the ileocecal valve.

Absorption in small intestine:

Small intestine:

The main digestion is Carrie out in small intestine and all of the absorption too. The small intestine has 3 parts:

• Duodenum (the part which receives the pancreatic secretion)
• Jejunum (main site for digestion of lipids and proteins along with carbohydrates)
• Ileum (it promotes only the process of absorption. There is almost no digestion there)

Digestion:

• Pancreatic juice contains many enzymes. Such as:
• Pancreatic amylase (for carbohydrates digestion)
• Pancreatic lipase (for fat digestion)
• Trypsinogen (for protein digestion; it is released in inactivated form but is activated by the intestinal enterokinase into trypsin)

Duodenum:

In duodenum, there is not much digestion. By the action of pancreatic juice a small proportion of starch is hydrolyze into maltose, proteins into peptones and polypeptides and fats into fatty acids and glycerol.

Jejunum:

Jejunum carries out the most of digestion. The enzymes act on the substrates and convert them into products:

• Amino peptidase converts polypeptides into dipeptides
• Erypsin converts dipeptides into amino acids
• Lipase converts fats into fatty acids and glycerol
• Maltase converts maltose into glucose
• Lactase converts lactose into glucose and galactose

Ileum:

Ileum is the site for absorption. All the digested carbohydrates, proteins and fats are absorber into the blood stream through the lacteals of intestinal villi especially fats in the form of lipoproteins or some by direct absorption e.g glucose and amino acids by active transport.

Conclusion:

In the light of above discussion we can say that Small intestine has very important role in the digestion and absorption of food. It has further three parts:

1. Duodenum
2. Jejunum
3. Ileum

And these parts have specific functions. If you want to know more about digestion in human body then click on this link and visit our article about complete basic digestion in our body.