SBP 3114 – RESPIRATORY, DIGESTIVE AND ENVIRONMENTAL SYSTEM

SALIVARY SECRETION

Introduction

Saliva is produced in and secreted from salivary glands. It contains many

important substances, including electrolytes, mucus, antibacterial compounds

and various enzymes. Saliva lubricates the mouth and starts the breakdown of

chewed food. The basic secretory units of salivary glands are clusters of cells

called ‘acini’. These cells secrete a fluid that contains water, electrolytes, mucus

and enzymes, all of which flow out of the acinus into collecting duct. Most

animals including human, have three major pairs of salivary glands that secrete

saliva:

Parotid glands

Submaxillary glands

Sublingual glands

Secretion of saliva is stimulated both by the sympathetic nervous system and

the para- sympathetic, which control both the volume and type of saliva

secreted. The saliva stimulated by sympathetic innervations is thicker, and

saliva stimulated parasympathetically is more watery. Potent stimuli for

increased salivation include the presence of food or irritating substances in the

mouth and thoughts of or the smell of food.

Diseases of the salivary glands and ducts are not uncommon in animal and man,

and excessive salivation is a symptom of almost and lesion in the oral cavity.

Methods and Materials

Materials:

Measuring cylinder, test tube and pipette

Rubber band and reading materials

Vinegar solution

Starch solution

Normal saline (0.9% NaCl)

Iodine solution

Tile

Toothpick

Methodology:

There are four different tests will be carried out for this experiment. Each test

needs one volunteer. Therefore four volunteers are needed and they need to

gargle with tap water before doing the experiment.

Test 1. Salivary secretion while resting:

Volunteer needs to stay still while reading (no voice) for 10 minutes.

Don’t swallow and spill out the saliva into measuring cylinder when

necessarily. Record the volume of saliva and keep it for further test (Test

5).

Test 2. Salivary secretion while chewing:

Volunteer needs to stay still while reading and chewing two rubber bands.

Collect the saliva for 10 minutes and keep it for further test (Test 5).

Test 3. Salivary secretion from chemical stimulation:

Volunteer needs to gargle with 0.5 ml of vinegar solution for 10 minutes.

Collect the saliva immediately after the solution was being discarded.

Record the volume of saliva for 3 minutes and keep it for further test (Test

5).

Test 4. Salivary secretion while talking:

Volunteer needs to talk to friend for 10 minutes. Collect and measure the

volume of saliva and keep it for further test (Test 5).

Test 5. Activity of Amylase Enzyme

Add 5 ml of starch solution into a test tube. Next, add 3 drops of saliva

and 9 drops of NaCl solution into the previous test tube. Mix them up and

then put one drop of mixture followed by iodine solution on tile every 30

seconds. Stir it with the toothpick. The presence of amylase enzyme in

saliva will convert starch to maltase while maltase will lead to changes of

iodine colour (yellow) to blue-black.

Record the time when the blue-black colour is not visible after the iodine is

added. Cancel the test if you still can see the colour after 15 minutes. Do

not use the same mixtures that have been added iodine.

Carry out this amylase enzyme activity test with the saliva that you have

collected before. Each group should have its own test tube.

Questions

A. Compare the volume of saliva that secreted on Test 1 - 4, and explain

the results that obtained.

B. Compare the activity of amylase enzyme in saliva on Test 1 - 4, and

explain the results that obtained.

30 seconds 30 seconds 30 seconds

1st well 2nd well 3rd well

1 drop of

iodine

1 drop of MIXTURE from the test tube

1 drop of iodine

1 drop of MIXTURE from the test tube

1 drop of iodine

Until 15 minutes or fully turned yellow

1 drop of MIXTURE from the test tube

MIXTURETest tube containing mixture of 5 ml starch, 3 drops saliva and 9 drops NaCl solution.

Stir with toothpick

Stir with toothpick

Stir with toothpick