Page 14 - 86 human physiology part-2

The Gastrointestinal System

The gallbladder stores bile, which is released when food containing fat enters the digestive tract,
stimulating the secretion of cholecystokinin (CCK). The bile emulsifies fats and neutralizes acids in
partly digested food. After being stored in the gallbladder, the bile becomes more concentrated than
when it left the liver, increasing its potency and intensifying its effect in fats.

Anus

The human anus is situated between the buttocks, posterior to the perineum. It has two anal
sphincters, one internal, the other external. These hold the anus closed until defecation occurs. One
sphincter consists of smooth muscle and its action is involuntary; the other consists of striated muscle
and its action is voluntary. In many animals, the anus is surrounded by anal sacs. Role of the anus is
when the rectum is full, the increase in intra-rectal pressure forces the walls of the anal canal apart
allowing the fecal matter to enter the canal. The rectum shortens as material is forced into the anal
canal and peristaltic waves propel the feces out of the rectum. The internal and external sphincters of
the anus allow the feces to be passed by muscles pulling the anus up over the exiting feces.

Conditions Affecting the Esophagus

There are two different types of conditions that may affect the esophagus. The first type is called
congenital: meaning a person is born with it. The second type is called non-congenital: meaning the
person develops it after birth. Some examples of these are:

Tracheoesophageal fistula and esophageal atresia

Both of these conditions are congenital. In Tracheoesophageal fistula there is a connection
between the esophagus and the wind pipe (trachea) where there shouldn't be one. In Esophageal atresia
the esophagus of a newborn does not connect to the stomach but comes to a dead end right before the
stomach. Both conditions require corrective surgery and are usually detected right after the baby is
born. In some cases, it can be detected before the baby is born.

Esophagitis

Esophagitis is inflammation of the esophagus and is a non-congenital condition. Esophagitis can
be caused by certain medications or by infections. It can also be caused by gastroesophageal reflux
disease (gerd), a condition where the esophageal sphincter allows the acidic contents of the stomach to
move back up into the esophagus. Gastroesophageal reflux disease can be treated with medications, but
it can also be corrected by changing what you eat.

Conditions Affecting the Stomach and Intestines

Everybody has experienced constipation or diarrhea in their lifetime. With constipation, the
contents of the large intestines don't move along fast enough and waste material stays in the large
intestines so long. All water is extracted out of the waste and it becomes hard. With diarrhea you get
the exact opposite reaction. Waste moves along too fast and the large intestines can't absorb the water
before the waste is pushed through. Common flora bacteria assists in the prevention of many serious

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