Download Digestive Tract from Cyber

Digestive Tract from Cyber-Anatomy Web site and Think Quest
The mouth and teeth are the first organs of the
digestive tract. The teeth are bones whose primary
purpose is to grind food in to easy bits that the
body can digest. In the mouth, saliva helps begin
to break down food. There are certain organs that
are located in the mouth, such as the uvula (the
“thing” that hangs down in the back of your
mouth) and the tongue. The walls of the inner
cheeks are lined with mucous which help protect
the food from bacteria, and also protect the cheeks
form saliva.
The pharynx is the passage way through which
many tubes run from the mouth and the nose to the
upper body. Some of these tubes are the
nasopharynx, which runs oxygen to the lungs, and
the oropharynx, which also runs oxygen to the
lungs.
The esophagus runs from the pharynx to the stomach. The Esophagus is about 25 cm ( 10
inches) long. The esophagus is really a large muscle which pushes food down to the stomach. The
walls of the esophagus are lined with four layers of thin tissue. These membranes are, the mucosa,
the submucosa, the muscularis externa, and the serosa.
The stomach is a J- shaped muscle. The stomach acts as a churn. There are two
sphincters, circular muscles that act as valves placed outside organs, surrounding the two openings
of the stomach. Chemical breakdown of food begins in the stomach.
The constant churning helps to improve digestion. There are several acids in the stomach. One
of these acids is known as gastric juice. Gastric juice is manufactured in gastric glands located in
the stomach. With gastric juice and other acids being mixed with the food, it breaks down and
become a creamy substance known as chyme. After being transformed into chyme, it goes into the
small intestine.
The small intestine is the primary organ of the of the digestive tract. In the small intestine, chyme is
finally broken down for its passage to cells. Bile is added to aid in digestion of fats. Bile is
manufactured in the liver. The small intestine may be subdivided into three segments. The first
segment of the small intestine is known as the deudodenum. The deudodenum is about 25 cm ( 10
inches ) long. The second segment of the small intestine is known as the jejunum. The jejunum is
about 2.5 meters ( 8 feet) long. The final segment of the small intestine is known as the ileum. The
ileum is about 3.6 meters (12 feet ) long. Since the small intestine can only process a small amount
of chyme at a time, the spchinter located at the beginning of the small intestine regulates the amount
of food that enters the small intestine.
In addition to digesting chyme, the small intestine is responsible for absorbing the processed
food into the bloodstream for delivery to the cells. This absorption takes place through structures
known as villi. Villi are finger like projections that increase surface area for absorption. The
unabsorbed chyme then passes to the large intestine.
The large intestine is about 1.5 meters ( 5 feet ) long. The large intestine stretches from a valve
that rests between the end of the small intestine and the beginning of the large intestine to the anus.
The main job of the large intestine is absorb water and to rid the body of any unwanted materials by
sending it to the anus. The large intestine has many subdivisions such as the cecum, the appendix,
the colon, the rectum, and the canal.