Page 10 - 86 human physiology part-2

The Gastrointestinal System

covered in projections called villi, which increase the surface area of tissue available to absorb nutrients
from the gut contents. It is different from the ileum due to fewer goblet cells and generally lacks
Preyer's patches.

The Ileum

Its function is to absorb vitamin B12 and bile salts. Thee 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 micro villi. The cells that line the ileum contain
the protease and carbohydrate enzymes 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.

Large Intestine

The large intestine (colon) extends from the end of the ileum to the anus. It is about 5 feet long,
being one-fifth of the whole extent of the intestinal canal. It's caliber is largest at the commencement at
the cecum, and gradually diminishes as far as the rectum, where there is a dilatation of considerable
size just above the anal canal. It differs from the small intestine in by the greater caliber, more fixed
position, sacculated form, and in possessing certain appendages to its external coat, the appendices
epiploicæ. Further, its longitudinal muscular fibers do not form a continuous layer around the gut, but
are arranged in three longitudinal bands or tæniæ.

The large intestine is divided into the cecum, colon, rectum, and anal canal. In its course, describes
an arch which surrounds the convolutions of the small intestine. It commences in the right iliac region,
in a dilated part, the cecum. It ascends through the right lumbar and hypochondriac regions to the under
surface of the liver; here it takes a bend, the right colic flexure, to the left and passes transversely
across the abdomen on the confines of the epigastric and umbilical regions, to the left hypochondriac
region; it then bends again, the left colic flexure, and descends through the left lumbar and iliac regions
to the pelvis, where it forms a bend called the sigmoid flexure; from this it is continued along the
posterior wall of the pelvis to the anus.

There are trillions of bacteria, yeasts, and parasites living in our intestines, mostly in the colon.
Over 400 species of organisms live in the colon. Most of these are very helpful to our health, while the
minority are harmful. Helpful organisms synthesize vitamins, like B12, biotin, and vitamin K. They
breakdown toxins and stop proliferation of harmful organisms. They stimulate the immune system and
produce short chain fatty acids (SCFAs) that are required for the health of colon cells and help prevent
colon cancer. There are many beneficial bacteria but some of the most common and important are
Lactobacillus Acidophilus and various species of Bifidobacterium. These are available as "probiotics"
from many sources.

Pancreas, Liver, and Gallbladder

The pancreas, liver, and gallbladder are essential for digestion. The pancreas produces enzymes
that help digest proteins, fats, and carbohydrates, the liver produces bile that helps the body absorb fat,

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