## Modeling the Alimentary Canal with String

The entire length of the adult GI tract from mouth to anus is approximately 9-10 meters in length. In this activity we will be measuring out the length of the gastrointestinal (GI) tract in a scaled version to compare the lengths of each section.  The scale model represents approximations of the length of each section of the GI tract.

Objectives:

1. Compare the lengths of each section of the GI tract
2. Trace the path of food through each section of the GI tract and label each section

1. Using the ruler or meter stick to measure 332 cm of string.  This may have been done for you.

2.  Measure 4 cm and make a line on the string with a marker. 0-4 cm represents the MOUTH.

3.  Starting from your 4 cm mark, measure out 9 cm.  The 4-13 cm represents the ESOPHAGUS.

4.  Starting from your 13 cm mark, measure out 8 cm,  13-21 cm represents the STOMACH.

5.  Starting from your 21 cm mark, measure out each of the following sections of the SMALL INTESTINE.
Duodenum = 15 cm           Jejunum = 100 cm      Ileum =  136 cm

6.  Starting at the end of the ileum, measure out each of the following sections of the  LARGE INTESTINE.
Ascending = 16 cm        Transverse = 16 cm         Descending = 11 cm         Sigmoid = 12 cm

7.  The last  5 cm represents the RECTUM.

8. Arrange your string flat (no overlapping) to represent the path of the alimentary canal. The string should fit the shape and direction of the sections. For example, the small intestine should zigzag to fit into the small space representing the abdomen  Construct your model and label each section.

Analysis

1)  Which section of the GI tract is the longest?   How does the length of this section relate to its function?

2) If the real GI tract is 9 meters long, the model you created is what fraction of the real one?
a)  ¼         b)    ½         c) ⅓              How do you know?

3)   There are four sphincter valves found in the GI tract, including the anus.  Describe the location of two of the sphincter valves found in the alimentary canal.

4)  One treatment for colon cancer is to remove the section that is cancerous.    Describe (or sketch) how the shape of the overall large intestine would change if the transverse colon was removed.