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Fu nctions Of The
Integumentary System
The skin functions in sensation, protection, thermoregu-
lation, and secretion.
Sensation
Receptor sites in the skin detect changes in the external
environment for temperature and pressure. Receptor sites
are in contact with sensory neurons that transmit the
impulse to the brain and spinal cord for interpreta-tion (see
Chapters 10 and 11). Temperature receptors produce the
sensations of hot and cold. Pressure recep-tor sites allow us
to interpret excessive pressure that re-sults in the sensation
of pain as when we get pinched. They also detect mild
pressure that results in the sen-sation of pleasure as from a
gentle massage or a petting stroke. Combinations of
varying degrees of those stimu-lations at these receptor
sites produce other sensations
Chapter 6that we call burning, itching, or tickling. These receptor
sites allow us to react to external stimuli and to interpret
what is occurring in the outside world.Protection
The skin is an elastic, resistant covering. It prevents passage of
harmful physical and chemical agents. The melanin pro-duced
by the melanocytes in the stratum germinativum darkens our
skin and protects us from the damaging ultra-violet rays of
sunlight. Most chemicals cannot gain -entry into the body
through the skin, but the chemicals that con-tain poison ivy
and poison oak can penetrate this barrier. Fat-soluble
chemicals like DDT, a chlorinated hydrocar-bon pesticide, can
also get through the skin. If you put your hand in a can of
gasoline, you will not be poisoned. How-ever, if you put your
hand in a container of DDT, you could be poisoned. People
who work with -certain insecticides must wear protective
clothing to prevent the penetration of these chemicals through
their skin.As The Body Ages
As we age, many visible changes occur in our skin such as crow’s feet around the
eyes and mouth. A decrease in secretions of sebum results in drier skin. We hear
and see advertisements for skin moisturizers, a big source of in-come for the
cosmetic industry. Loss of collagen and elastin fibers in the dermis results in the
skin sagging and wrinkling. Blood flow to the skin decreases with age, and the skin
becomes thinner and looks more trans-lucent. The number of melanocytes
decreases in certain areas, causing the darkening appearance of other areas of
the skin referred to as age spots^
or liver spots. Lack of melanin also affects the graying and production of white hair with increased
age.
As we age, hair does not grow as regularly on our heads as it did in our youth, and many
people, females as well as males, experience thinning hair or baldness. This is also related- to
genetic factors. Some individuals experience baldness as early as their 20s whereas others
maintain a full head of hair into their 70s.
Nails, especially fingernails, may become brittle and break easily, while both fingernails and
toenails can become susceptible to fungal infections and become discolored and thicker than
normal.
Older adults may become sensitive to the cold due to poor blood circulation in the der-mis
and fewer fat deposits underneath the skin for insulation in the subcutaneous layer. In addition,
due to the skin not being able to repair and maintain itself as easily as it did in youth, infections of
the skin are more likely to develop in older adults.
There is less sebum secretion from the sebaceous glands later in life, resulting in drier skin
and hence the need for skin moisturizers. During the winter months in north temperate climates,
this condition is further exaggerated by drying winds, resulting in cracked skin with small, open,
and painful wounds around the tips of fingers. During these times, daily applica-tions of hand
cream moisturizers are especially helpful.