Everything about Ileum totally explained
In
anatomy of the
digestive system, the
ileum is the final section of the
small intestine. It is about 2-4 m long in
humans, follows the
duodenum and
jejunum, and is separated from the
cecum by the
ileocecal valve (ICV). The
pH in the ileum is usually between 7 and 8 (neutral or slightly alkaline).
Function
Its function is mainly to absorb
vitamin B12 and
bile salts and whatever products of digestion that were not absorbed by the jejunum. The wall itself is made up of folds, each of which has many tiny finger-like projections known as
villi, on its surface. In turn, the epithelial cells which line these villi possess even larger numbers of
microvilli. Therefore the ileum has an extremely large surface area both for the
adsorption (attachment) of
enzyme molecules and for the absorption of products of
digestion. The DNES (diffuse neuroendocrine system) cells that line the ileum contain the protease and carbohydrase enzymes (gastrin, secretin, cholecystokinin) responsible for the final stages of
protein and
carbohydrate digestion. These enzymes are present in the
cytoplasm of the
epithelial cells. The villi contain large numbers of capillaries which take the amino acids and glucose produced by digestion to the
hepatic portal vein and the liver.
Lacteals are small lymph vessels, and are present in villi. They absorb
fatty acid and
glycerol, the products of fat digestion. Layers of circular and longitudinal
smooth muscle enable the digested food to be pushed along the ileum by waves of muscle contractions called
peristalsis.
Differences between jejunum and ileum
There is no line of demarcation between the jejunum and the ileum. There are, however, subtle differences between the two.
- The ileum has more fat inside the mesentery than the jejunum.
- The ileum is a paler color, and tends to be of a smaller caliber as well.
- While the length of the intestinal tract contains lymphoid tissue, only the ileum has abundant Peyer's patches.
These unencapsulated
lymphoid nodules contain large amounts of
lymphocytes and other cells of the
immune system.
Embryology
In the
fetus the ileum is connected to the
navel by the
vitelline duct. In roughly 3% of humans, this duct fails to close during the first seven weeks after birth, causing a condition called
Meckel's diverticulum.
Veterinary anatomy
In veterinary anatomy, the ileum is distinguished from the jejunum by being that portion of the jejunoileum that's connected to the
caecum by the
ileocaecal fold.
Additional images
Image:Gray1044.png|Inferior ileocecal fossa.
Image:Gray536.png|Arteries of cecum and vermiform process.
Image:Gobletcel.jpg|Goblet cell in ileum
Image:Gut wall.svg|General structure of the gut wall.
Further Information
Get more info on 'Ileum'.
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