bowel
Meaning of bowel: Nearly all nutrition is taken up in the first section, while the second exists largely to reclaim water before waste is passed.
Definition of bowel
The bowel is the long tube of the digestive tract running from the stomach to the anus. The small bowel, where almost all nutrient absorption takes place, leads into the large bowel, which reclaims water and salts and forms and stores stool. Bowel and intestine name the same structure.
What are its parts?
| Segment | Main job |
|---|---|
| Duodenum | Receives stomach contents together with bile and pancreatic enzymes; most iron and calcium are taken up here |
| Jejunum | Where the bulk of sugars, amino acids and fats are absorbed |
| Ileum | Reclaims bile salts for reuse and takes up vitamin B12, which no other segment can absorb |
| Colon | Reclaims water and salts from what remains and houses most of the gut bacteria |
| Rectum | Stores stool until it is passed |
How does it absorb so much?
Surface area is the answer. The lining of the small bowel is thrown into circular folds, those folds are covered in finger like projections called villi, and each cell on a villus carries a dense brush of even smaller projections. The result is an absorbing surface out of all proportion to the length of the tube. Enzymes sit on that brush border to finish breaking down sugars and proteins at the moment of uptake, and a rich blood and lymph supply immediately beneath carries the products away. Absorption also depends on movement: rhythmic muscular waves mix contents with digestive juices and push them along at a pace that allows contact without stagnation.
What do the bacteria do, and what goes wrong?
The colon holds an enormous bacterial population that ferments the fiber human enzymes cannot break down, producing short chain fatty acids that the colon lining itself uses as fuel, and contributing some vitamin K. Disturbing that population, most commonly with antibiotics, allows less welcome organisms to take over. Because the bowel is long, thin walled and constantly working, a wide range of problems affects it: infection, obstruction by scar tissue or a tumor, twisting, interrupted blood supply, and the lifelong inflammation of inflammatory bowel disease. Where the trouble sits determines what is noticed, since problems high up cause vomiting and poor absorption while problems low down change the bowel movement itself.
Also known as
Used in a sentence
Imaging was ordered to evaluate for a possible bowel obstruction after the patient reported abdominal distension.
Good to know
The terms bowel and intestine are generally used interchangeably, though bowel is more common in everyday clinical usage and intestine more common in formal anatomical description.
Word origin
Where “bowel” comes from
From Latin botellus, a diminutive of botulus, meaning sausage, by way of Old French boel.