The Digestive System An Overview by xuyuzhu


									The Digestive System: An Overview
   Life is all about using energy. The energy that your body uses comes from the food
        you eat. This food or fuel is broken down to release its energy and to create
        building blocks for cell growth and repair in the digestive system.

  The digestive system makes your body somewhat like a donut with a hole running all
       through you body. This hole is called the digestive tract and is composed of
       numerous parts. Look at the diagram on page 847 and list what each of the
       following parts do.
Oral Cavity




Small intestine

Large intestine

   In addition to this hole you have accessory organs that help the digestive tract do its
        job. List the accessory organs and say what they do.

   Read about the functions of the digestive system on page 846 and summarize each in
        the space below.
1. Ingestion

2. Mechanical Processing

3. Digestion
4. Secretion

5. Absorption

6. Excretion

   If you cut the digestive tract crosswise, you will discover that it has four layers
        including (1) the mucosa, (2) the submucosa, (3) the muscularis externa, and (4)
        the serosa. Read about each of these layers and complete the table below:

Wall Layer                     Subdivisions of the layer     Major Functions


Muscularis externa

    The two layers of smooth muscle in the muscularis externa play an important role in
        moving material along the digestive tract. The two layers are arranged in
        different directions. The Inner layer is arranged so that the muscle fibers run in a
        ____________ while the outer layer has muscle fibers that run

    The contractions of these two layers create two different kinds of movement.
        Movement through _______________ helps move material along the tract and
        _________________ helps in the mechanical processing of material.

    Describe these two kinds of movement below:



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