1. I. Functions of the Digestive System
       
A. Functions-
1. Digestion:
The process by which
your body Breaks down
food into small nutrient
molecules.
(mechanical and chemical)

2. 2. Absorption: The process by which nutrient molecules
pass through the wall of your digestive
system into your blood.

3. 3. Elimination:
Materials that are not absorbed are eliminated from the body as waste (ie. Fiber)

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II. Types of Digestion:
Mechanical – foods are physically broken down into smaller pieces
Chemical – chemicals produced by the body break foods into smaller chemical building blocks
Both begin in the mouth.

5. III. The Process of Digestion
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III. The Process of Digestion
The Mouth
Mechanical Digestion
Teeth cut food into bite-size pieces, then crush and grind them into smaller pieces.
Saliva mixes with and moistens the food as you chew to aid you in swallowing.
Chemical Digestion
Saliva contains chemicals called enzymes which are proteins that speed up chemical reactions in the body.
The enzymes break down starches into sugar molecules.

6. A muscular tube that connects the mouth to the stomach.
B. Esophagus
A muscular tube that connects the mouth to the stomach.
a. It’s lined with mucus, which allows food to move easily through the esophagus.
At the top of the esophagus, there is a flap of tissue called the epiglottis. It covers the opening to your trachea (windpipe) when you swallow so that you don’t choke on your food.
a. Food remains in the esophagus for about 10 seconds.
b. After food enters the esophagus, contractions of smooth muscles push the food toward the stomach. (Peristalsis)

7. Stomach
A J-shaped, muscular pouch located in the abdomen.
Most mechanical digestion and some chemical digestion
Mechanical – Three strong layers of smooth muscle surround the stomach and contract to churn the food. This mixes it with fluids that further the digestion process.
Chemical – The churning of mechanical digestion mixes the food with strong enzymes that continue to break down food.
Hydrochloric acid (HCl) in your stomach, provides the ideal environment for the enzymes for proteins to work.
Food remains in the stomach for about three hours. When it is a thick liquid, it is ready to move to the next section of the digestive system.

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Small Intestine
The part of the digestive system where the most chemical digestion and absorption of nutrients takes place.
The digestion of fats takes place here.
Several secretions get added here from other organs. (Liver and Pancreas)
The small intestine is lined with millions of tiny projections (villi) that help increase the surface area for the absorption of nutrients from your food.

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Liver
The role of the liver in the digestive system is to produce bile
Bile is a substance that breaks up fat particles. It is not an enzyme, but it does break up large fat molecules into small fat droplets which can be broken down easier.
Bile is stored and concentrated in the gallbladder.

10. Pancreas
The pancreas produces enzymes that flow into the small intestine and help break down starches, proteins, and fats.
It also produces insulin which regulates the amount of sugar in your blood.

11. The small intestine is where fat digestion takes place, however all nutrients are digested in the small intestine.
The tiny projections inside of the small intestine are called villi. Villi increase the surface area to absorb more nutrients.
Bile is a chemical made by the liver that breaks down fat molecules into smaller fat molecules.
Bile is stored and concentrated in the gallbladder.

12. Large Intestine
The large intestine is the last section of the digestive system.
The large intestine contains bacteria that feed on materials as they pass through. Many of them make vitamins like vitamin K.
Water is absorbed from the digested food materials into the bloodstream.
The large intestine ends in a tube called the rectum, which is where wastes are compressed into solid form.