Fundamentals of Anatomy and Physiology

The Integumentary System

The lipid content of the skin inhibits the excessive loss

of water and electrolytes through the skin. Normal skin is

impermeable to water, carbohydrates, fat, and protein.

However, all true gases and certain volatile substances will

pass through the epidermis like the or-ganic pesticide just

mentioned. The numerous openings around hair follicles

can act as channels for absorption of these materials.

Skin also has an “acid mantle.” This acidity kills most

bacteria and other microorganisms that make contact with

our skin. Soaps and shampoos will often be labeled as pH

balanced, which indicates that these cleansers will not

destroy the acid mantle of the skin. Some skin diseases will

destroy the acidity of certain areas of the skin, impair-ing

the self-sterilizing capabilities of our skin. These dis-eases

make the skin prone to bacterial infections.

Nails protect the ends of our digits. Fingernails can

also be used in defense. Hair on our head acts as an

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insulator and helps prevent heat loss. Hairs in our nose

filter out large foreign particles like soot. Eyelashes pro-

tect our eyes from foreign objects.

Thermoregulation

Normal body temperature is maintained at approxi-mately

98.6°F (37°C). Temperature regulation is critical to our

survival because changes in temperature affect the

functioning of enzymes. The presence of enzymes is

critical for chemical reactions to occur in our cells, since

enzymes act as protein catalysts to speed up chemi-cal

reactions under normal cellular conditions. When people

get high fevers, they can die because the heat of a fever

destroys the enzymes by breaking up their chemi-cal

structure. Without enzymes, chemical reactions can-not

occur and our cellular machinery breaks down and death

results.

Common Disease, Disorder, or Condition

SKIN CANCER

Skin cancer usually develops from excessive exposure to the ultraviolet rays of the sun,
which is the reason sunscreens with an SPF of 15 or above should be used when
engaging in outdoor recreational activities, or when one’s occupation requires out-door
work. Common areas of development of skin cancers are the face, neck, and hands.
There are three types of skin cancers, two of which can be lethal.^
The most common type of skin cancer is basal cell carcinoma. This cancer
-produces an open ulcer and can be easily treated with radiation therapy or surgical
removal. This cancer rarely spreads. The first dangerous type of skin cancer is
squamous cell carcinoma, which produces a nodular tumor that is highly keratinized
and found in the epidermis (Figure 6-6). If untreated it can spread to the dermis,
-metastasize, and cause death. The most dangerous type of skin cancer is malignant
melanoma (Figure- 6-7). It is rare and associated with a mole on the skin. A mole is a
grouping of melanocytes. They become cancerous and metastasis is common. The
melanoma can appear as a dark nodule or a spreading flat lesion. Unless treated early,
this cancer is fatal.

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Figure 6- 6 Squamous cell carcinoma on the face. Figure 6- 7 Facial malignant melanoma. (^)