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The jejunum is the second part of the small intestine, connecting the duodenum with the ilium. It is also the longest section of the small intestine, commonly comprising almost half its length. This area of the intestines is supplied with blood by the superior mesenteric artery, and is held in place by the mesentery, part of the peritoneum which lines the stomach cavity. Rather than being firmly positioned, the jejunum is actually suspended, which allows it to move within the stomach cavity as digestive processes occur.
This area of the small intestine has a very large surface area, created in part by folds of tissue. Projections known as villi also increase the surface area of the jejunum, with each projection sticking up like a small finger. The villi are responsible for absorbing nutrients, with the jejunum being the area in which absorption begins in the small intestine. Reuptake of bile also occurs in the jejunum.
The jejunum also secretes digestive enzymes which break down foods into units which can be absorbed by the intestine. This enzyme secretion, which actually starts in the stomach, is a key part of digestion. Without digestive enzymes, the intestine cannot actually access many of the nutrients in food, and thus will not be able to utilize food for nutrition. Impairments in nutrient production caused by congenital conditions or disease can be a source of malnutrition for a patient.
It is sometimes necessary to remove all or part of the jejunum. One cause for removal is the growth of a cancer which compromises the small intestine, and another is traumatic injury so severe that it cannot be repaired. If the blood supply to this area of the intestine is cut off, this can also necessitate removal, as parts of the jejunum may die if the blood supply is cut off for too long. Removal is performed by a surgical team with the patient under general anesthesia.
When parts of the jejunum are removed, patients must take special precautions. They are at risk of malnutrition both because they are missing an area of the intestine where absorption occurs, and because they may not be producing all of the enzymes they need. Some dietary modifications may be necessary to ensure that the patient gets proper nutrition, and the patient will be given specific advice by a doctor to learn what to eat and when, and to find out about supplementation options which will keep the patient's body nourished.
@irontoenail - The way our teacher tried to get us interested in the jejunum and ileum was to tell us about how, if you got hit with a lot of force in that area, you would end up vomiting. It's a reflex known as emesis.
Of course, then we all went around threatening each other with emesis (jokingly of course!) for the next few days, but at least we remembered the word!
The other thing she told us was that sausage casings are made from parts of the intestine from farm animals. Not always, because sometimes they use artificial ones now, but more often than not.
I think quite a few people in the class looked at sausages with different eyes after that!
The jejunum is that long squishy part of the intestine that looks like it is kind of stuffed underneath the more muscular looking ileum.
We studied it in one of my biology classes. I guess I quite liked the name, which means "hungry" in old English.
Apparently since they used to find this part of the stomach empty when people died, they called it that. My teacher always tries to give us a little bit of information like that to make the word easier to remember.
The jejunum is usually about 2.5m long, which is kind of crazy, because that's quite a lot longer than your whole body.