What is absorbed in the small intestine

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With m y CHP, you can request appointments, review test results, and more. To pay your bill online, please visit UPMC's online bill payment system. Support the hospital by making a donation online , joining our Heroes in Healing monthly donor program , or visiting our site to learn about the other ways you can give back. Our Sites. Intestine Transplant. What Is the Small Intestine? The small intestine is made up of three segments, which form a passage from your stomach the opening between your stomach and small intestine is called the pylorus to your large intestine: Duodenum: This short section is the part of the small intestine that takes in semi-digested food from your stomach through the pylorus, and continues the digestion process.

The duodenum also uses bile from your gallbladder, liver, and pancreas to help digest food. Jejunum: The middle section of the small intestine carries food through rapidly, with wave-like muscle contractions, towards the ileum.

Ileum: This last section is the longest part of your small intestine. The ileum is where most of the nutrients from your food are absorbed before emptying into the large intestine. How can the small intestine digest so much?

The small intestine has three features which allow it to have such a huge absorptive surface area packed into a relatively small space: Mucosal folds: The inner surface of the small intestine is not flat, but thrown into circular folds. This not only increases the surface area, but helps regulate the flow of digested food through your intestine.

Villi: The folds form numerous tiny projections which stick out into the open space inside your small intestine or lumen , and are covered with cells that help absorb nutrients from the food that passes through. If individuals who are deficient do not receive injections of the vitamin they may experience severe negative consequences, including dementia. Digestive activity in the stomach provokes the gastroileal reflex, which stimulates peristalsis to push contents along the ileum and the colon.

The reflex ensures that the content of one meal is completely emptied from both the stomach and the small intestine before the next meal is eaten. It can take up to five hours for all chyme to leave the small intestine Young et al, When most of the chyme has been absorbed, the walls of the small intestine become less distended and segmentation gives way to peristalsis, which helps move unabsorbed matter along towards the large intestine. Peristalsis works a little like squeezing toothpaste along and out of a tube.

With each repeated peristaltic contraction, chyme and waste slowly move down the small intestine. When motility in the ileum increases, the ileocaecal valve relaxes, allowing food residue to enter the large intestine at the caecum.

Tagged with: Newly qualified nurses: systems of life. Sign in or Register a new account to join the discussion. You are here: Gastroenterology. Gastrointestinal tract 4: anatomy and role of the jejunum and ileum. Abstract After its passage through the duodenum, where most chemical digestion takes place, chyme passes through the jejunum and ileum. This article has been double-blind peer reviewed Scroll down to read the article or download a print-friendly PDF here if the PDF fails to fully download please try again using a different browser Click here to see other articles in this series.

Also in this series Gastrointestinal tract 1: the mouth and oesophagus Gastrointestinal tract 2: the structure and function of the stomach Gastrointestinal tract 3: the duodenum, liver and pancreas Gastrointestinal tract 5: the anatomy and functions of the large intestine Gastrointestinal tract 6: the effects of gut microbiota on human health.

References Hall JE Digestion and absorption in the gastrointestinal tract. Philadelphia, PA: Saunders. Keuchel M et al Normal small bowel. Medicine ; 4, Gut ; 12, Welcome MO Structural and functional organization of the gastrointestinal tract. Cham: Springer International Publishing. Wilson M The indigenous microbiota of the gastrointestinal tract. Oxford: Wiley-Blackwell. Young KA et al The small and large intestines. In: Anatomy and Physiology.

Related files. The remaining chyme and water pass to the large intestine, which completes absorption and eliminates waste. Villi that line the walls of the small intestine absorb nutrients into capillaries of the circulatory system and lacteals of the lymphatic system. Villi contain capillary beds, as well as lymphatic vessels called lacteals.

Fatty acids absorbed from broken-down chyme pass into the lacteals. Other absorbed nutrients enter the bloodstream through the capillary beds and are taken directly to the liver, via the hepatic vein, for processing. Chyme passes from the small intestine through the ileocecal valve and into the cecum of the large intestine.

Any remaining nutrients and some water are absorbed as peristaltic waves move the chyme into the ascending and transverse colons. This dehydration, combined with peristaltic waves, helps compact the chyme. The solid waste formed is called feces. Key Points Digested food is able to pass into the blood vessels in the wall of the small intestine through the process of diffusion. The inner wall, or mucosa, of the small intestine is covered in wrinkles or folds called plicae circulares that project microscopic finger-like pieces of tissue called villi, which in turn have finger-like projections known as microvilli.

Each villus transports nutrients to a network of capillaries and fine lymphatic vessels called lacteals close to its surface. Key Terms villi : Tiny, finger-like projections that protrude from the epithelial lining of the intestinal wall. The Small Intestine The small intestine is the part of the gastrointestinal tract between the stomach and the large intestine where much of the digestion of food takes place.

Absorption of the majority of nutrients takes place in the jejunum, with the following notable exceptions: Iron is absorbed in the duodenum. Vitamin B12 and bile salts are absorbed in the terminal ileum.