Human Body: Jejunum and Ileum
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Human Body: Jejunum and Ileum

The small intestine in the human body has three parts, including the long narrow tube consisting of the jejunum and ileum. The jejunum and ileum have a similar structure, but each has a particular function in the digestion of food and absorption of nutrients.

The human digestive system consists of the mouth, esophagus, stomach, small intestine, large intestine, and rectum. The small intestine is a long, narrow tube that is coiled inside the abdomen. It is anchored to the spine, though it has a great deal of freedom of movement in response to the other organs in the human body.

The purpose of the small intestine is to break down partially digested food from the stomach so the human body can absorb and use the different nutrients in the food. The undigested remainder is then passed into the large intestine.

Structure of the Small Intestine

The small intestine has 3 parts:

  • Duodenum
  • Jejunum
  • Ileum

The jejunum is 3 to 6 feet long, and the ileum can be 6 to 12 feet. Both the jejunum and ileum have a diameter of about 3 to 4 centimeters, or about 1.5 inches. This is much less than the diameter of the large intestine, which is why one portion of the intestine is labeled “small” and the other “large,” even though the large intestine is shorter, with only 5 feet or less of length.

The structure of the jejunum and ileum is similar. Both have a series of wrinkles, or rugae, along their interior surface, as well as tiny finger-like projections called villi and microvilli. Villi in the ileum are shorter. These tiny projections increase the area of absorption inside the small intestine. In fact, the surface area created by the rugae, villi, and microvilli is equal to a tennis court.

Function of the Jejunum and Ileum

The jejunum and ileum have some separate functions, however. The jejunum is largely responsible for digesting and absorbing proteins, carbohydrates, and fats from the partially digested food material that leaves the stomach. It breaks down these components in food by releasing enzymes. The process is further aided by enzymes from the pancreas and liver. Proteins are broken down into amino acids, carbohydrates are turned into simple sugars, and lipids become fatty acids and glycerol.

The ileum is responsible for absorbing vitamin B-12 and bile salts. The lining of the ileum is more porous than that of the jejunum, allowing bile to be absorbed and returned to the liver. The ileum is also differentiated from the jejunum by the presence of Peyer’s patches. This lymphatic tissue is part of the gastrointestinal immune system that identifies and destroys potentially harmful microorganisms passing through the gut.


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Comments (5)

excellent my friend

I have learned added info on the issue of digestive system, thanks Shav.

I appreciate your kind words Carol and Ron. Many thanks.

That's something to contemplate. This just shows that our body is wonderfully made.

Patrick, Yeah, I was startled to learn that I had the area of a tennis court in the middle of my gut!