Biology

The human body consists of number of organ systems which work collectively to execute functions of the body. The three most important human organ systems are circulatory, digestive and endocrine system. The main function of the digestive system is to process food in such a way that the energy molecules are absorbed by the body and the residues are left out. The physiological processes which are required for the digestive system are absorption, digestion, motility, secretion and excretion (Margaret E. Smith, 2001)

Digestive System
Digestive system helps the body to maintain stability, equilibrium or balance. Digestive system contributes in homeostatic regulation of the body. The body would suffer if there is no regular supply of energy and nutrients from digestive system. The digestive system helps in absorption of ions, vitamins, organic substances and water that is necessary to the body. When the food is chewed and swallowed, the food is broken down in the digestive tract to very small nutrient molecules which can be easy to enter into the villi of small intestine. (Rebecca L.Johnson, 2004) Digestive enzymes are formed by the pancreas and the digestive tract. Besides this, the liver produces bile which is stored in the gall bladder to digest the fats. By the use of hepatic portal vein, blood passes from smaller intestine to the liver i.e., in to the circulatory system. The liver is the vital organ of homeostasis and it monitors the blood. The liver produces urea by breaking down toxic substances like alcohol and other drugs. After eating, the liver stores glucose as glycogen and produces plasma proteins. Liver keeps the blood glucose concentration constant by releasing glucose in between eating. This is how the digestive system works along with the other systems which include circulatory system.

Organs in the Digestive system
There are several organs in the digestive system. The digestive system can be divided in to two systems. They are upper gastrointestinal tract and lower gastrointestinal tract. The upper gastrointestinal tract consists of several organs like mouth, oral cavity, pharynx, esophagus and stomach. The lower gastrointestinal tract consists of small intestine, ileum, large intestine, anus and rectum. (Cheryl Jakab, 2007) The functions of some important organs include

Oral Cavity
The oral cavity or the mouth is the first part of the digestive system. It accepts food by way of ingestion. Here, the food will be broken in to smaller pieces and get mixed with saliva. Saliva helps as lubrication for the food particles. The oral cavity consists of different parts which are helpful in the digestive system. They are tongue and teeth.

Small Intestine
The small intestine is about 35 millimeteres in length and grayish purple in color. The small intestine is the longer intestine which is six to seven meters long. The small intestine has the general structure of the GI tract. The small intestine consists of exocrine cells in the mucosa which secretes peptidase, mucus, maltase, sucrose, lipase, maltase and enterokinase. Endocrine cells secrete secretin and cholecystokinin.

The process of digestion is completed by the small intestine. It absorbs the nutrients and sends the residue to large intestine. The gall bladder, liver and pancreas are important organs in the digestive system which is closely related to the small intestine. Small intestine is divided in to duodenum, jejunum and ileum. The small intestine helps in several functions such as hormone secretion, intestinal juice secretion, ninety percent absorption, forward propulsion of contents and it is the major site of digestion.

Rectum
The rectum can be found in the lowest portion of the large intestine which connects to the anus and it is a muscular tube like structure. The waste is stored here and permits expulsion when pressure on the rectal walls is caused.

Anus
The anus is formed by the surface layers of the body, skin and the intestine. The anus is the opening at the end of the digestive tract through which the waste matter is ejected from the body.

There are many diseases which are caused due to the improper functioning of the digestive system. The most specific disease is the Ulcer. Ulcer is the disorder caused in the upper digestive tract. Ulcer can be developed in the duodenum, lower part of the esophagus and in jejunum. There are many causes for ulcer. Some of them include certain medications, infection and disorders caused by the over secretion of stomach juices. The symptoms of gastric ulcer include weight loss, feeling heart burn and indigestion and gastrointestinal bleeding.  Most of the patients suffering from ulcer suffer from bleeding which results in vomiting blood, anemia or blood through rectum.