intestine
Meaning of intestine: Packed into the abdomen in coils, the intestine offers a surface area for absorption far larger than its outward size suggests.
Definition of intestine
The intestine is the long, folded tube in the abdomen that completes digestion after food leaves the stomach. It has two connected sections. The small intestine, the longer and narrower of the two, absorbs most nutrients into the bloodstream. The large intestine reclaims water and salts from what remains and compacts it into stool.
What does each section do?
The small intestine comes first, running from the outlet of the stomach to the start of the large intestine. It is the longer of the two but the narrower, and it is where almost all nutrient absorption happens. Its lining is thrown into folds, and those folds are carpeted with finger-like projections, giving an internal surface out of all proportion to the length of the tube. Digestive juices from the pancreas and bile from the liver enter near its beginning. What is left by the end is mostly water, fiber, shed cells and bacteria.
The large intestine receives that residue. It is shorter and wider, and its work is subtraction rather than nutrient uptake: water and certain salts are drawn back into the body and the contents thicken from liquid toward solid. It also houses a dense bacterial population that ferments fiber the body cannot break down on its own.
Why does the affected section change the symptoms?
| Small intestine | Large intestine | |
|---|---|---|
| Relative length | Longer | Shorter |
| Caliber | Narrower | Wider |
| Chief role | Absorbing nutrients | Absorbing water, forming stool |
| Effect of a blockage | Vomiting early, cramping around the navel | Swelling and constipation first, vomiting late |
An obstruction illustrates the point. A blockage high in the narrow small intestine backs contents up toward the stomach quickly, so vomiting comes early. A blockage low in the wide large intestine allows a long stretch of bowel to fill first, so distension of the abdomen and an inability to pass stool or gas come first instead.
How does material move through it?
Contents advance by peristalsis, rings of muscle in the wall tightening behind the contents and relaxing ahead of them. The pace differs by section. Material crosses the small intestine in a matter of hours, while passage through the large intestine is measured in a day or more, and that slower transit is what allows time for water to be reclaimed. Hurried movement leaves stool loose because digestion and reabsorption both need contact time; sluggish movement leaves it dry and hard for the same reason in reverse.
Also known as
Used in a sentence
Imaging was obtained to evaluate the cause of the patient's intestinal obstruction.
Good to know
The small intestine is primarily responsible for nutrient absorption, while the large intestine mainly reabsorbs water and forms stool, a distinction that helps explain why disease in one segment produces different symptoms than disease in the other.
Word origin
Where “intestine” comes from
From Latin intestinus, meaning internal, derived from intus, meaning within.