1. Lab 10 – Mechanical Digestion (Part II)
Dr. Kim Wilson

2. Introduction – Part I (Mechanical Digestion)
Mechanical digestion physically changes foods from large pieces into small minute pieces. This process occurs throughout the GI tract along with the process of chemical digestion.

3. Part A (Dissolving a Life Saver)
INSTRUCTIONS:
1. Obtain 2 baby food jars. Label one A, the other B. Add 25 cc's warm water to each. (Use the same temperature of water in each.)
2. Obtain and add one whole life saver to Jar A, and at the same time, add one crushed life saver to Jar B. Record the time on the Results Sheet. Gently swirl each jar once.
3. Allow the jars to set undisturbed and observe how long it takes each life saver to dissolve. Record the results on the Results Sheet.
4. Answer related questions on the Questions Sheet.

4. Part B - Introduction
Swallowing is a complex process that requires the co‑ordination of many muscles and other structures in the head and neck. The process must occur both smoothly and rapidly since respiration is inhibited for 1‑3 seconds while food clears the pharynx.

5. Part B Instructions
Take 2 or 3 swallows from a glass of water, and note the movement of your tongue. In which direction does the tongue move each time the water is swallowed? Record the results on the Results Sheet.
Place your fingers gently on your larynx and swallow more water. Note its movements. Take a firm hold of the larynx and try prevent its moving while you swallow. Record the results on the Results Sheet.
Most acoustical stethoscopes have both diaphragm and bell type heads for detecting sounds of different frequency. Using both heads, listen for swallowing sounds on the front and sides of the neck, and over the cardiac sphincter valve as your partner swallows more water. The earpieces should fit snugly into the ears and enough pressure applied to the diaphragm or bell to ensure firm contact with the skin. Don't allow the stethoscope tubing to touch or rub against any firm surface as you listen. This will cause noise that will mask the swallowing sounds. Record the results on the Results Sheet.
Bend from the waist and swallow normally. With your partner's help, attempt to drink water from a cup (while bending). Record the results on the Results Sheet.
Answer related questions on the Questions Sheet.

6. Part 2 – Chemical Digestion
Chemical digestion begins in the mouth when salivary glands are stimulated to secrete saliva. Saliva contains an enzyme which aids in the digestion of starch.

7. Part 2 Instructions
1. Chew some paraffin so that you will reflexly produce a large amount of saliva. Collect approximately 10 cc's of this saliva in a small beaker. Using litmus paper, determine the pH of the saliva. (Litmus paper turns blue in alkaline conditions and red in acid conditions.) Record the pH on the Results Sheet.
2. Place 5 cc's of a boiled starch suspension into each of two test tubes. Label the test tubes as 1 and 2.
3. Add 1 drop of 2% Tincture of Iodine to each test tube. Record the results on the Results Sheet.
* Note: Starch + Iodine = Blue/Black Color
4. Add 20 drops of saliva to test tube 1. Record the time on the Results Sheet.
5. Add 20 drops of water to test tube 2. Record the time on the Results Sheet.

8. Instructions cont.
6. Place both of the test tubes in a beaker and incubate for 1 hour at 37 C. Record the beginning incubation time on the Results Sheet.
7. After the 1 hour incubation period, gently swirl each test tube and observe for color changes. Record these changes on the Results Sheet.
8. If the suspension in one of the test tubes is colorless or lighter in color, proceed to step 10. If no changes in color have occurred in either test tube, proceed to step 9.
9. Add 12 more drops of saliva to test tube 1 and 12 more drops of water to test tube 2. Incubate for 30 more minutes. Gently swirl each test tube and record the results on the Results Sheet.
10.Add 5 cc's of Benedict's solution to each test tube and place them in a boiling water bath for 2 minutes. USE CAUTION TO AVOID INJURY.
11.Remove the test tubes from the water bath and gently swirl. Observe for any of the following color changes:

9. Results ‑ Solution Remains Blue (No Sugar Present) + Green Solution
++ Yellow Solution
+++ Orange Solution
++++ Red Solution
If solution turns green, yellow, orange, or red, sugar is present and the amount varies from 1+ (small amount) to 4+ (large amount).
Record the results on the Results Sheet.
12.Answer related questions on the Questions Sheet.

10. Part B – Digestion in the Stomach
1. Complete the sheet titled, "Student Guide ‑ Digestion Biokit: Gastric Digestion". Record the results in the spaces indicated and include in your lab report.
2. Answer related questions on the Questions Sheet.