Small Intestine Function, Parts with Facts

With respect to digestion and absorption of nutrients, small bowel is the most important part of gastrointestinal system in humans and other higher animals. It is the segment of gut that lies between pyloric sphincter (the posterior end of stomach) and the junction at cecum where it is followed by the last part of digestive system, that is, large bowel. Though the length of small intestine varies greatly from an individual to the other, on average it is about 22 feet 6 inches in human adults while in females, it is usually a bit larger, i.e. 23 feet and 4 inches. In extreme variations, it may reach the length of 32 feet or can be as shorter as just 8 feet.

Small Intestine

Parts of Small Intestine

To enjoy an ideal health and counter the diseases, you must have sound knowledge of different parts of the small intestine with facts. Small bowel is further divided into three structurally and somewhat functionally distinguishable smaller segments, viz. duodenum, jejunum and ileum. In various segments, the three layers of its wall are similar throughout its length, but there do exist certain structural differences among them.


Duodenum-The foremost and shortest part of small intestine, it is functionally very important as major portion of the chemical digestion takes place here. Varying in length from 10 to 15 centimeter, it is, on the anterior end, connected with stomach, while the posterior end touches jejunum.


Jejunum-The second part of your small bowel, located between duodenum and ileum, its average length in adult human is about 8.4 feet or two and a half meter. The pH of the medium inside this part of gut may vary between neutral to slightly alkaline, i.e. 7 to 9. The enterocytes are the specialized cells present in the lining of the canal that are actively involved in the absorption of small particles of food that were digested by enzymes in duodenum.


Ileumb-The final section of small gut that, on one hand, continues with jejunum, while on the other hand makes a connection with colon through ileocecal valve. In adult humans, it may vary from 7 to 14 feet in length, and the pH of the medium is same as that of jejunum which is neutral to a bit alkaline. Its major function is to absorb any nutrients that were not absorbed in the preceding sections of the gut; however, it is particularly involved in the absorption of bile salts and vitamins (vitamin B12).

Functions of Small Intestine

Functionally, small bowel is very important part of gastrointestinal tract as it not only digests major part of the dietary contents but is also meant for absorbing finally digested food particles. It is the place where almost all of the absorption takes place including nutrients, bile salts, vitamins, and so on. Some of the major small intestine functions can be listed as under:


The partly digested food that is coming from stomach through pyloric opening is highly acidic in its medium, but the enzymes present in duodenum and other parts of small intestine cannot perform their activity as biological catalysts in it. So as the first and foremost function of the gut, this medium is neutralized and the enzymes are made to act in the most efficient way.


After the medium has been made feasible for the enzymatic actions, the digestion of the remaining contents of chyme is accomplished here. Different secretions are poured into small gut, like bile and pancreatic juice that facilitate the overall process of breakdown to a greater extent, until the finally digested food particles are ready to be absorbed.


Here it is surprising to know that among all the segments of gut, this is the only portion where almost all of the absorption of digested food, vitamins and salts, takes place. For the intake of nutrients into the bloodstream, there are specialized cells (e.g. enterocytes) that facilitate the process of absorption. After entering the bloodstream, the food particles are delivered to all the living cells in the body where, by means of metabolic reactions, energy is extracted from them to accomplish all the vital activities.