Human Digestive System

Introduction:

There are a lot of organs make up the digestive tract. They are mouth, esophagus, stomach, small intestine, large intestine (also called the colon) and anus. The digestive system also includes organs that lie outside the digestive tract: the pancreas, the liver, and the gallbladder. The job of each of these organs is to break food down, so that it's small enough to be absorbed and used by the body for energy or in other bodily functions.


Definition:
The group of organs that break down food and absorb the nutrients used by the body for fuel. The organs in the digestive system, in the order in which food travels through them, are:
  • Mouth
  • Esophagus
  • Stomach
  • Small Intestine
  • Large Intestine
  • Rectum
  • Anus

Human_Digestive_System.gif
Picture of Human Digestive System

Why is digestion important?

When you eat foods. For example, meat, and vegestables- they are not in a form that the body can use as nourishment. Food and drink must be changed into smaller molecules of nutrients before they can be absorbed into the blood and carried to cells throughout the body. Digestion is the process by which food and drink are broken down into their smallest parts so the body can use them to build and nourish cells and to provide energy.

How is food digested?

Digestion involves mixing food with digestive juices, moving it through the digestive tract, and breaking down large molecules of food into smaller molecules. Digestion begins in the mouth, when you chew and swallow, and is completed in the small intestine.








http://www.youtube.com/watch?v=Z7xKYNz9AS0


Absorption and Transport of Nutrients

Most digested molecules of food, as well as water and minerals, are absorbed through the small intestine. The mucosa of the small intestine contains many folds that are coverd with tiny fingerlike projections called villi. In turn, the villi are covered with microscopic projections called microvilli. These structures create a vast surface area through which nutrients can be absorbed. Calls allow absorbed materials to cross the mucosa into the blood.

Carbohydrates

Carbohydrates
Carbohydrates include bread,potatoes,dried peas, beans, rice,pasta,fruits,and vegetables.
The digestible carbohydrates - strach and sugar - are broken into simpler molecules by enzymes in the saliva, in juice produced by the pancreas, and in the lining of the small intestine. Stra is digested in two steps. First, an enzyme in the saliva and pancreatic juice breaks the starch into molecules called maltose. Then an enzyme in the lining of the small intestine splits the maltose into glucose molecules that can be absorbed into the blood. Glucose is carried throught the bloodstream to the liver, where it is stored or used to provide energy for the work of the body.
Sugar
Sugar are digested in one step. An enzyme in the linking of the small intestine digests sucrose,into glucose and fructose, which are absorbed through the intestine into the blood. Milk contains another type of sugar, lactose which is changed into absorbable molecules by another enzyme in the intesinal lining

Fiber
Fiber is undigestible and moves through the digestive tract without being broken down by enzymes.
Protein
Foods such as meat, eggs and beans consist of giant mocecules of protein that must be digested by enzymes before they are be used to build and repair body tissues. An enzyme in the juice of the stomach starts the digestion of swallowed protein. Than in the small intestine complete the breakdown of huge protein molecules into small molecules called amino acids. These small molecules can be absorbed through the small intestine into the blood and then be carried to all parts of the body to build the walls and other parts of cells.
FatsFat molecules are a rich source of energy for the body. The first step in digestion of a fat such as butter is to dissolve it into the watery content of the intestine. The bile acids produced by the liver dissolve fat into tiny droplets and allow pancreatic and intestine enzymes to break the large fat molecules into smaller ones.
Vitamins
Another vital part of food that is absorbed through the small intestine are vitamins. The two types of vitamins are classified by the fluid in which they can be dissolved: water-soluble vitamins (all the B vitamins and vitamins C) and fat-soluble vitamins (vitamins A,D,E, and K). Fat- soluble vitamins are stored in liver and fatty tissue of the body, whereas water-soluble vitamins are not easily stored and excess amounts are flushed out in the urine.
Water and Salt
Water and salt. Most of the material absorbed through the small intestine is water in which salt is dissolved. The salt and water come from the food and liquid you swallow and the juices secreted by the many digestive glands.

How is the digestive process controlled?

The major hormones that control the functions of the digestive system are produced and released by cells in the mucosa of the stomach and small intestine. These hormones are released into the blood of the digestive tract, travel back to the heart and through the arteries, and return to the digestive system where they stimulate digestive juices and cause rogan movement. The main hormones that control digestive are gastrin, secretin, and cholecystokinin (CCK).


conclusion
Summary of digestive Secretions
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The digestive system plays a very important role in the functioning of the human body in that it regulates the energy break down for the cells of the body. Without the digestive system, the cells of the body would not be able to obtain the energy needed for proper functioning.

Bibliogrogph:
http://www.contmediausa.com/shop/app/products/Human3D/human3ddigestivesystem.html

http://en.wikipedia.org/wiki/Carbohydrate
http://www.carbs-information.com/digestion-of-carbs.htm
http://www.youtube.com/watch?v=Z7xKYNz9AS0&feature=related
http://www.mhhe.com/biosci/ap/dynamichuman2/content/digestive/visuals.mhtml