Bodily Defenses Image Map



Why do we need a digestive tract?
If the body did not have a digestive tract, you could not enjoy your favorite pizza, hamburger, or other food.  The human body must obtain its energy by eating food. Therefore, the main purpose of the digestive system is to provide the body with amino acids, carbohydrates, fats, and vitamins to keep our cells functioning.  The digestive system provides these essential materials to the 75 trillion cells that live in our bodies. Wow! Do you know how many 75 trillion is?

The digestive tract takes both liquids and food and breaks them down into single molecules that can be absorbed by cells in the small intestine. These cells transport the molecules into the blood stream so that other cells in the body can use them. The digestive tract also serves to eliminate what your body doesn't absorb during the digestive process.

Why do I have a stomach?
The stomach has two major functions in your body: one for digestion and one for defense.  (See the illustration on the right.). Digestion breaks down proteins with acidic stomach juice, secreting enzymes that split up proteins into individual amino acids (see Cells Are Us unit on proteins).  The defense component kills most foreign organisms that you ingest so that they can't get into your bloodstream or anywhere else in your body.  These organisms are destroyed by the highly acidic stomach fluid that is secreted within the stomach.  

Why do you have two intestines?
The intestines are where the body absorbs all of the food, vitamins, fluid, and minerals that you eat.  The intestines are long giving your body a greater opportunity to absorb more of what you eat. The small intestine breaks down proteins, carbohydrates, and fats so that they can be absorbed into the body and the bloodstream. The large intestine is where moisture is absorbed from what is left of the food. Anything that is not absorbed by the intestines is then passed through as solid waste (or feces).

Why are the liver and pancreas important in digestion?
Your liver secretes bile into your small intestine.  This bile contains worn out red blood cells that must be removed from the body. If the old red blood cells are not removed, they can become toxic.  The bile secreted by your liver also separates the fats that you eat so that they can be broken down by enzymes.   (See the picture on the right.) Fat clumps together and when bile is not secreted into the small intestine, your enzymes are less efficient at breaking down fats into their fatty acid components.  

The enzymes that break down these separated fats come from the pancreas, as do those enzymes that break down carbohydrates and proteins.  The pancreas also secretes a basic solution that neutralizes the acidic solution left over from the stomach.  

The pancreas also secretes insulin, which helps move glucose (blood sugar) from blood into cells. Diabetes is a common and very serious disease that results from lack of insulin. For more information about diabetes, click here.



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