THE DIGESTIVE SYSTEM

DESCRIPTION

The digestive system consists of an alimentary canal with accessory organs . The
alimentary

canal is made up of the oral cavity , pharynx , esophagus , stomach , and small intestine ,
which

has three parts , the duodenum , jejunum , and the ileum ,the large intestine which consists
of

the cecum and the vermiform appendix , the ascending colon , transverse colon , the
descending

colon , the sigmoid colon , the rectum and anal canal .The accessory organs are the teeth ,

tongue, salivary glands , sublingual , submandibular , and parotoid , the liver , gall bladder
or

cystic duct, the common bile or hepatic duct , the pancreas , and the spleen .

FUNCTION

The digestive systemís function is to break down foods into nutrients such as proteins ,
fats ,

and carbohydrates .It supplies the various organs with energy and nutrients , vitamins , and

minerals . The digestive system breaks down food into particles so tiny that blood can take

nourishment to all parts of the body .

PHYSIOLOGY

The digestive process begins in the oral cavity , where food is cut , ground , and shredded
by the

teeth .The salivary glands lubricate the food as it is swallowed into the esophagus and
slides to

the stomach . The food bolus is retained there , the food is then liquefied by a mixture of
hydro-

cloric acid and pepsin , which is secreted by the stomach wall . Secretions of mucus
protect the

the stomach from itís digestive enzymes . The food is then pushed out of the stomach by

peristalsis where it enters the duodenum , the first third of the small intestine .The small
intestine

is 16 to 20 feet in length and has an absorbing surface equivalent to half a basketball court
.

Nutrient absorption occurs mostly in the small intestine .Peristalsis moves the chyme to
the
jejunum , the second part of the small intestine .The bulk of digested carbohydrate ,
protein ,

water , water-soluble vitamins , electrolytes , and minerals are absorbed . The remaining

nutrients are propelled to the last third of the small intestine , the ileum . Fat , fat-soluble
vita-

mins A , D , E , K , and B12 are absorbed here .Some indigestible remains and cellular
debris

are sent to the colon . Additional water is extracted , potassium is excreted and all this is
sent to

the rectum for evacuation .The feces is metabolic end product , water , fats , electrolytes ,
and a

small amount of protein . The body then uses and burns all the useable materials and the
cycle

is repeated .

DISEASE

There are a variety of diseases that plague the digestive system . Ulcers are not
uncommon and

may be minor or very serious . If an ulcer is ignored it can lead to death .Gallstones are
hard

masses found in the gallbladder .They can be treated with surgery or drugs .Dysentery
causes

painful diarrhea , bloating and cramps .Appendicitis is a dangerous but curable diseases by
way

of surgery . A patient with appendants can live only a few days