Physio Lab Report

Experiment No. 7

PHYSIOLOGY OF THE SKIN

I. Materials Needed:

Glass plates, Two squares of bond papers (1cm x 1cm each), adhesive tape, betadine or Lugol's solution, Cotton Swab

II. Procedures:

A. Visualizing Changes in Skin Color Due to Continuous External Pressure

1. Obtain a small glass plate or watch glass.

2. Press the heel of your hand firmly against the plate for a few seconds.

3. Observe and record the color of your skin in the compressed are by looking through the back of the glass.

Questions:

1. What is the color of the compressed skin?

2. What is the reason for this color change?

What would happen if the pressure was continued for an external period in this area?

3. Cite three abnormal variations in skin color and the indicative condition associated with them.

B. Plotting the Distribution of Sweat Glands

1. Obtain two squares of bond paper (1cm x 1cm), adhesive tape and a betadine solution or Lugol's iodine and cotton-tip swab.

2. Using the iodine solution, point an area of the medial aspect of the left palm (avoid the crease line) and a region of the left forearm. Allow the iodine solution to dry thoroughly. The painted area in each case slightly larger than the paper squares to be used.

3. Mark one piece of ruled bond paper with an "ll" for hand and the other "A" (for arm). Have your laboratory partner securely tape the appropriate square of board paper over each iodine-painted area, and leave them in place for 20 minutes. (If it is very warm in the laboratory, good results can be obtained within 10-15 minutes).

4. After 20 minutes, remove the paper squares and count the number of blue-black c=dots in each square. The appearance of the blue-black dot on the paper indicates an active sweat gland. (The iodine in the pore dissolves in the sweat and reacts with the starch in the paper to produce the blue-black color). Thus sweat "maps" have been produced for the skin areas.

Questions:

1. Which skin area tested has the most number of sweat glands?

2. In what specific areas in the body are sweat glands absent?

3. Explain how the skin, through sweating, can participate in thermoregulation?

4. Describe the chemical composition of sweat produced by ecrine sweat glands with that produced by the apocrine sweat glands.

Regine Marie E. España

BS PH III

I. Introduction

The skin is far more than just the outer covering of human beings. The skin consists of two layers, the epidermis and the underlying dermis. Besides providing a layer of protection from pathogens, physical abrasions, and radiation from the sun, the skin serves many functions as well as playing a vital role in homeostasis. In response to high environmental temperature or strenuous exercise, the evaporation of sweat from the skin surface helps lower an elevated body temperature to normal. In response to low environmental temperature, production of sweat is decreased, which helps conserve heat. Changes in the flow of blood to the skin also help regulate body temperature. The skin covers the body and provides a physical barrier that protects underlying tissues from physical abrasion, bacterial invasion, dehydration, and ultraviolet (UV) radiation. Hair and nails also have protective functions. The skin contains abundant nerve endings and receptors that detect stimuli related to temperature, touch, pressure, and pain. Certain cells of the epidermis are important components of the immune system, which fends off foreign invaders. The dermis of the skin houses extensive networks of blood vessels that carry 8 to 10% of the total blood flow in a resting adult. In moderate exercise, skin blood flow may increase, which helps dissipate heat from the body. During hard exercise, however, skin blood vessels constrict (narrow) somewhat, and more blood is able to circulate to contracting muscles. Metabolism of vitamin D occurs in the skin, as well.

In the experiment, an external