Explore the different parts of human digestive system

Date:28/6/08 SAT

I decided to find out more about the parts of the digestive system and their uses so as to compare with the digestive system with carnivore and herbivore.

Firstly, let start with the mouth, as digestion begins in it. The function of the mouth and its associated structures is to help us chew our food into smaller pieces and, mix the food with saliva,which will soften the food with the help of the tongue, and then swallow it into the gullet.

The gullet will then carries food and water to the stomach for more digestion. Powerful waves of muscle contractions passing through the walls of the gullet helps the food to be forced downward to the stomach.

In the stomach, food is further broken apart, and thoroughly mixed with a gastric acid and digestive enzymes that break down proteins. Besides digesting the food , it has several more functions: 1) as a storage bin, holding a meal in the upper portion and releasing it a little at a time into the lower portion for processing; 2) as a food mixer, the strong muscles contract and mash the food into a sticky, slushy mass; 3) as a sterilizing system, where the cells in the stomach produce an acid which kills germs in "bad" food.

Next, the food will enter the small intestine. The the duodenum in the small intestine breaks down the food mixture even more so our body can absorb all the vitamins, minerals, proteins, carbohydrates, and fats. Then, most of the nutrients are absorbed into the blood in the jejunum.
The ileum absorbs the remaining nutrients before moving into the large intestine. All the nutrients will come in contact with large numbers of intestinal cells and it will bring in fresh, oxygenated blood and sends out nutrient-enriched blood to the body for energy to do work. Substances which have not been absorbed in the small intestine enter the large intestine in the form of liquid and fiber.

The first half of the large intestine absorbs fluids and recycles them into the blood stream.After that, the second half will then compact the wastes into feces, secretes mucus which binds the substances, and lubricates it to protect the colon and ease its passage.The feces is stored in the rectum for a certain period and then the stored feces is egested due to the contraction and relaxation through the anus.

Therefore, I can conclude that digestion is separated into four separate processes:

1. Ingestion: placing food into the mouth
2. Mechanical digestion & chemical digestion: mastication to tear and crush food, and churning of the stomach. Addition of chemicals to break down complex molecules into simple structures
3. Absorption: Movement of nutrients from the digestive system to the circulatory system.
4. Egestion: Removal of undigested materials from the digestive tract through defecation.

The next reserach i am going to do would be the digestive system in a herbivore. Off i go for more mad research...