Parts of the Digestive system and their Functions

joeldgreat By joeldgreat, 18th Nov 2010 | Follow this author | RSS Feed | Short URL http://nut.bz/1ywdz94c/
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Identify the parts of the digestive system and describing each one.

Introduction

All the parts of the digestive system form a coiled tube. This tube is called the alimentary canal or digestive tract. The food we eat passes through this tube during the process of digestion so that it can be changed into simpler substances that can be used by all our body cells. The parts of the digestive system differ in their structure and function.

Mouth

The mouth is the first part of the digestive tract. The tongue and the teeth are found in the mouth. The inside of the mouth is lubricated with saliva that comes from the salivary glands. The strongest muscles are found in each side of the mouth. They help move the lower jaw and give it a biting force.

There are four types of teeth in the mouth. The incisors are used in cutting food. The canines are used for grasping, piercing and tearing. The premolars and molars are used for crushing and grinding. Aside from tasting food, the tongue is used for moving the food as the saliva softens it. We have three pairs of salivary glands. Saliva from these glands lubricates the food and makes it soft. Saliva also contains an enzyme that breaks down starch.

Esophagus

From the mouth, food goes down the esophagus through the pharynx or throat. The esophagus is a muscular tube that can open and close at the pharynx. It can also open and close to the stomach. The walls of the esophagus consist of smooth muscles. The wavelike movement of these muscles, called peristalsis, pushes the food down to the stomach.

Stomach

The stomach is a hollow muscular organ shaped like a bag. Its upper end is connected to the esophagus while the lower end is connected to the small intestine. The upper and lower ends of the stomach have smooth circular muscles called sphincter muscles. When the upper end muscle relaxes, the stomach opens and food gets in. When the lower end muscles relaxes, partially digested food moves out of the stomach. The sphincter muscles keep the food in the stomach.

The stomach is flexible and can expand when you eat. It can hold from 1 to 3 liters of food. The stomach acts as a storage bag of food. If the stomach could not store food, you would have to eat every twenty minutes or so instead of just three times a day. The stomach contains three layers of smooth muscles which also produce peristaltic movements to continue breaking down the food.

Intestines

The intestines are found below the stomach and liver. They form the major part of the digestive tract. The small intestine is about 2.5 centimeter in diameter and 6 meters long. Its wall are made of smooth muscles. The inner lining of the small intestines is folded into tiny fingerlike projections called villi (singular, villus). Each villus contains blood vessels. The work of the small intestines is to digest food, which can then be absorbed by the blood. The villi act much like the same as the folded towels. Because the wall of the intestine is folded into millions of villi, the surface area through which nutrients pass to the bloodstream is greatly increased. If the villi on the inner lining of the small intestine are flattened out, they would cover about 4500 square meters.

The large intestine is about 5 centimeters in diameter and about 1.8 meters long. Its main part if the colon. At the end of the colon is the rectum which opens to the anus. The work of the large intestine is to absorb water from the undigested food, hold the undigested food for a while and then excrete it as feces.

Accessory Parts of the Digestive System and their functions

The liver, pancreas and gall bladder are not part of the alimentary canal but they have important functions in the digestive process. They are called accessory parts of the digestive system.

Liver
The liver lies under the diaphragm and near the stomach. It is the largest organ inside the body and one of the most important. Among the functions of the liver that are related to digestion are the following.
1. It produces bile, a substance that helps in the digestion of fats.
2. It stores glycogen, vitamins and some minerals, such as iron and copper, which are released when needed by the body.

Gall bladder
The gall bladder is a small muscular sac that is attached beneath the liver. Bile produced by the liver passes through a small tube and is stored in the gall bladder. From the gall bladder, bile is released to the small intestine digestion.

Pancreas
The pancreas is an organ that lies behind the stomach. Its function related to digestion is to produce pancreatic juice. Pancreatic juice helps in neutralizing or weakening the acid in food inside the stomach before it moves onto the small intestine. Pancreatic juice also contains different enzymes that are needed to further break down starch, proteins and fats in the small intestine.


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Tags

Alimentary Canal, Digestive System, Esophagus, Gall Bladder, Intestines, Liver, Mouth, Pancreas, Stomach

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