one-third of the people who try it, many find the hair
growth to be meager. This drug will not help individuals
who are already bald.
Glands Produce Secretions That
Perform a Variety of Functions
Three types of glands are associated with the skin
(
Figure 4.4
):
Sebaceous glands (
se-BA-shus
) secrete
sebum,
an oily
substance containing lipids and cellular debris. Sebum
softens skin, prevents hair from drying out, and prevents
water loss from the body surface. When sebaceous glands
of the face become enlarged because of accumulated
sebum,
blackheads
develop.
Bacteria
metabolize
the
sebum and form pimples or boils (especially in the skin
of the forehead, palms, and soles).
Sudoriferous glands (
soo'-dor-IF-er-us
) are sweat glands.
Sudoriferous glands come in two varieties:
eccrine
and
apocrine.
The eccrine sweat glands are distributed all over
the body and produce a watery sweat that helps regulate
body temperature. The apocrine variety is limited to the
axillary and pubic regions and produces a thicker sweat
often released during emotional stress. This sweat is
composed mostly of water but also contains electrolytes
(sodium, potassium, chloride, calcium, magnesium, trace
elements) and certain waste materials (lactate, urea).
Ceruminous glands
(
se-ROO-mi-nus
)
are modified
sweat glands found in the ear canal and outer ear. They
secrete
earwax,
or
cerumen
(
se-ROO-men
). Cerumen is
composed of lipids and cellular debris, forming a sticky
barrier
that
both waterproofs
and inhibits
debris,
foreign objects, insects, and microbial organisms from
entering the ear canal.
G lands o f th e skin
• Figure 4.4
a. The major glands of the skin include the oil glands
b.
, c. Two types of sweat glands
a.
Sebaceous oil glands lie in the dermis and
open into hair follicles or directly onto the skin.
They secrete oily sebum, which does the
following:
• Keeps hair from drying out
• Prevents excessive water evaporation from
the skin
• Keeps skin soft
• Inhibits growth of certain bacteria
b.
Eccrine sudoriferous sweat glands
are found throughout the body.
• Secretory portion in the deep dermis
• Open directly to the outside through pores
• Secrete sweat in response to rise in temperature and
emotions
• Sweat is mostly H2O, Na+, Cl-, urea, ammonia, amino
acids, glucose, and lactic acid
• Remove heat by evaporation, thereby cooling the skin
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c. Apocrine sudoriferous sweat glands
are found in axillae,
groin, areolae, and beards.
• Secretory portion in subcutaneous layer
• Open into hair follicle
• Secrete viscous milky or yellow sweat in response to
emotions (for example, fear, embarrassment, sexual activity)
• Sweat is similar to eccrine sweat but also contains lipids and
proteins
• Sweat interacts with bacteria and produces body odor
98
CHAPTER 4
The Integumentary System
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