Digestive System

Mechanical Digestion
Mechanical Digestion takes place in the mouth, where the saliva, teeth, and tongue all play important roles in the digestive process.

Saliva: The most simple taste, sight, and anticipation of food sends a signal to the brain to ready increased saliva production. Salivary enzymes produce pytalin which breaks down food to a more simple form.

Teeth: As we all know, teeth are the workforce behind the digestion of food. Strong muscles crush and tear food for easier digestion.

Tongue: The tongue is a strong, pliable arragngement of muscle consisting of sweet, sour, salty, and bitter taste buds. The tongue helps remove particles from teeth, and arrange food in mouth.

The Digestive Process:
The start of the process - the mouth: The digestive process begins in the mouth. Food is partly broken down by the process of chewing and by the chemical action of salivary enzymes, these enzymes are produced by the salivary glands and break down starches into smaller molecules).

On the way to the stomach: the esophagus - After being chewed and swallowed, the food enters the esophagus. The esophagus is a long tube that runs from the mouth to the stomach. It uses rhythmic, wave-like muscle movements (called peristalsis) to force food from the throat into the stomach. This muscle movement gives us the ability to eat or drink even when we're upside-down.

In the stomach - The stomach is a large, sack-like organ that churns the food and bathes it in a very strong acid (gastric acid). Food in the stomach that is partly digested and mixed with stomach acids is called chyme.

In the small intestine - After being in the stomach, food enters the duodenum, the first part of the small intestine. It then enters the jejunum and then the ileum (the final part of the small intestine). In the small intestine, bile (produced in the liver and stored in the gall bladder), pancreatic enzymes, and other digestive enzymes produced by the inner wall of the small intestine help in the breakdown of food.

In the large intestine - After passing through the small intestine, food passes into the large intestine. In the large intestine, some of the water and electrolytes (chemicals like sodium) are removed from the food. Many microbes (bacteria like Bacteroides, Lactobacillus acidophilus, Escherichia coli, and Klebsiella) in the large intestine help in the digestion process. The first part of the large intestine is called the cecum (the appendix is connected to the cecum). Food then travels upward in the ascending colon. The food travels across the abdomen in the transverse colon, goes back down the other side of the body in the descending colon, and then through the sigmoid colon.

The end of the process - Solid waste is then stored in the rectum until it is excreted via the anus.

All information is from http://www.enchantedlearning.com/subjects/anatomy/digestive/