Digestive+System+HW+CC

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 * Digestive System Book Homework (p.144-155)**

3. Describe the mechanical digestion and the chemical digestion that occurs in the mouth.
-Mechanical digestion starts when we begin chewing food in our mouths right as we enter it. The teeth help move the food around in the mouth and break it down some. The tongue then helps shape the chewed food into a mass called a bolus, which it then passes toward the pharynx. - Chemical Digestion is the break down of foods by enzymes and there are enzymes in the saliva that break down sugars.

4. What ordinarily prevents food from entering the nose or entering the trachea when you swallow?
- The glottis is the opening to the larynx, which is the voice box. When we swallow, the epiglottis is supposed to cover and close off the opening (the glottis) to the larynx so food can't go down this way. Your soft palate moves back and covers the opening in the mouth to the nose.

5. What are the function of the stomach, and how is the wall of the stomach modified to perform these functions?
- The stomach's main purposes are to store food, start the digestion of proteins, and control the movement of chyme into the small intestine. The stomach is surrounded by a wall made up of the 4 usual layers, but two of them have been modified. Instead of just 2 layers of smooth muscle, the muscularis has 3 smooth layers of muscle. This allows the stomach to stretch and break down the food and liquids in to smaller sizes. The mucosa is different in the stomach in that it has deep folds and also has gastric glands which produce the enzyme pepsin. Pepsin breaks down proteins.

6. What are the functions of the small intestine and how is the wall of the small intestine modified to perform these functions?
- Food enters the small intestine after it has gone through the stomach. It enters the small intestine as chyme in squirts from the stomach. Digestion is finalized in the small intestine because it contains enzymes that are able to do the final breaking down of foods. These enzymes are made by the pancreas. The small intestine wall absorbs sugars, amino acids, lipids. The mucosa of the small intestine contains villi (little projections) which help absorb nutrients.

7. What are the three main accessory organs that assist with the digestive process?
-The three main accessory organs are the pancreas, the liver, and the gall bladder.

8. How does each accessory organ contribute to the digestion of food?

 * The pancreas produces digestive enzymes which are released in to the small intestine and are able to break down all kinds of food.
 * The liver helps to filter blood in capillaries and also stores iron and other vitamins.
 * The gall bladder stores bile from the liver until it is sent by the bile ducts to the small intestine. Bile helps digest fat.

10. What are the functions of the large intestine?
- The large intestine helps prevent dehydration of the entire body by absorbing water. It also absorbs vitamins, but does not break down anything or absorb any nutrients.