Fundamentals of Anatomy and Physiology

The Integumentary System

or cat looks after a good brushing. The coat of fur glistens
and shines due to the sebum.
Sebaceous secretion is under the control of the
endocrine system. It increases at puberty, resulting in acne
problems in adolescents, and it decreases in later life,
resulting in dry skin problems. It also increases in late
pregnancy. Modified sebaceous glands line the ear canal
and are called ceruminous glands. They produce earwax or
cerumen.

Sweat Glands

Sweat glands (see Figure 6-1) are simple tubular glands
found in most parts of the body. They are not found on the
margins of the lips or the head of the penis. They are most
numerous in the palms of our hands and in the soles of our
feet. It has been estimated that there are 3000 sweat glands
per square inch on the palms of our hands. When you get
nervous, think about which area of your body gets sweaty
first —your hands!
Each sweat gland consists of a secretory portion and an
excretory duct. The secretory portion is located in the deep
dermis, occasionally in the subcutaneous tissue, and is a
blind tube twisted and coiled on itself. A blind tube is one
that has only one opening, in this case at the top. From the
coiled secretory portion that produces the sweat, the
excretory duct spirals up through the dermis into the epi-
dermis and finally opens on the surface of the skin.
The most common and most numerous type of sweat
glands are referred to as eccrine (EK-rin) sweat glands.
Another smaller group of sweat glands are called apocrine
(AP-oh-krin) sweat glands. These are found only in the
armpits, in the scrotum of males, in the labia

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majora of females, and around the anus. They are not

involved in regulating body temperature. They usually open

into hair follicles just above the sebaceous gland. They

become active at puberty and contribute to the de-

velopment of body odor.

Sweat contains the same inorganic materials as blood

but in a much lower concentration. Its chief salt is sodium

chloride, which is the reason sweat tastes salty. Its organic

constituents include urea, uric acid, amino acids, ammonia,

sugar, lactic acid, and ascorbic acid. Sweat itself is

practically odorless. That may surprise you because many

of us have been in a locker room at a gym. Actually the

odor is produced by the action of bacteria feeding on the

sweat. Remember the last time you did some strenuous

exercise? You were sweating but there was no odor for the

first 10 or 15 minutes. After that time, odor developed

because it took that long for the bacte-rial population to

grow in the sweat and their effects to be smelled.

Sweating is also an important physiologic process that

cools the body. Sweating leads to loss of heat in the body

because heat is required to evaporate the water in sweat.

Therefore, sweating helps lower body tempera-ture. Some

people are born without sweat glands—they have a

congenital absence of these glands. These indi-viduals can

easily die of heat stroke if exposed to high temperatures

even if only for a brief period of time. Other individuals

have overactive sweat glands and must use stronger

deodorants and antiperspirants. Due to hair in the armpits,

sweat accumulates there. Because our armpits are usually

covered while our arms are at our sides, the environment is

ideal for bacteria to feed on the sweat, hence the need for

deodorants.

Health Alert

ACNE IN ADOLESCENTS

During puberty, the sebaceous glands

secrete- an excessive amount of sebum. The

opening of the gland can become clogged with

this oily substance. -Because so much is

being secreted, it cannot make its way onto

the surface of the skin. The fatty oil oxidizes in

the presence of air and becomes discolored,

producing a “­blackhead.” The sebum retained

in the gland can provide- a growth medium for

pus-producing bacteria-. If the clog is near the

surface

of the skin, this results in a pimple. If the clog

is deep in the gland along the shaft of the hair,

the result is a boil. This must be lanced by a

physician so that it can be drained of excess

fluid and the bacterial infection.

To prevent blackheads and pimples,

-adolescents should frequently wash their

faces on a regular daily basis. They may use

astringents like alcohols to dry the surface of

their skin, depending on skin type.