Bodily Defenses Image Map
Digestive Structures and Functions
Over the years scientists have learned a lot about the digestive tract that has given doctors and researchers in the health science field the necessary information to cure or treat most of the digestive disorders that face us today. 


Digestive Structures & Functions
Liver's Role in Digestion
Large Intestine

Is pizza good for me? 
Pizza contains the three major types of food your body needs to function and some essential vitamins, but it also contains cholesterol, which can cause blockage in your blood vessels.  Pizza is very high in calories and fat.

Food in pizza

Nutrients in the food


Fats and fat-soluble vitamins

Meats (pepperoni, sausage, etc.)
Proteins, minerals
Tomato Sauce & Vegetables
Carbohydrates and water soluble vitamins

(To learn more about proteins, carbohydrates, and fats visit: Cells are Us)

What organs are involved in digestion?
Many organs are involved in the digestive process (see the diagram on the
left). First, food enters the body via the mouth, where saliva from the salivary gland begins to break down carbohydrates. Next, the food goes down the food tube, the esophagus, pushed by muscular contractions. The food ends up in the stomach, where stomach acids breakdown much of the protein into amino acids and kill most bacteria in the food. The liver processes and regulates the substances entering the blood stream from the food that is ingested. The liver also produces bile, which contains worn-out red blood cells, that is stored in the gall bladder. The pancreas assists in digestion of carbohydrates, proteins, and fats, and it regulates blood sugar levels by directing cells to take up or to secrete sugar into the blood. Once leaving the stomach, the food travels into the small intestine where carbohydrates, amino acids and fats are absorbed. After entering the large intestine, moisture is absorbed from what is left of the food and bacteria breaks down some of the material that has not been digested. This creates waste (feces). The rectum is the final storage space for wastes, which is what becomes of the food once all of the nutrients and moisture have been removed. The wastes remain in the rectum until excreted.

The time food stays in the various parts of the digestive tract in a human under normal conditions is approximately as follows:

  • Stomach: 4-6 hours

  • Small intestine: 2-4 hours

  • Large intestine: 24-48 hours

Knowing this, you should be able to answer the following:

  1. Why do you get hungry at the times for breakfast, lunch, and dinner?

  2. Why should you have a bowel movement every day or two?

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