Integumentary System
any young people are all too famil-
iar with
acne vulgaris,
a disorder of
the sebaceous glands. Excess sebum
and squamous epithelial cells clog the glands,
producing blackheads and whiteheads (come-
dones). The blackness is not dirt but results from
the accumulated cells blocking light. In addition,
the clogged sebaceous gland provides an attrac-
tive environment for anaerobic bacteria. Their
presence signals the immune system to trigger
ammation. The inF
amed, raised area is a pim-
ple (pustule).
A Hormonal Problem
Acne is the most common skin disease, affect-
ing 80% of people at some time between the
ages of eleven and thirty. It is usually hormonally
induced. Just before puberty, the adrenal glands
increase production of androgens, which stimu-
late increased secretion of sebum. At puberty,
sebum production surges again. Acne usually
develops because the sebaceous glands are
extra responsive to androgens, but in some cases,
androgens may be produced in excess.
Acne can cause skin blemishes far more seri-
ous than the perfect models in acne medication
ads depict (±
g. 6C). Scarring from acne can lead to
emotional problems. ²ortunately, several highly
ective treatments are available.
What to Do—And Not Do
Acne is not caused by uncleanliness or eating too
much chocolate or greasy food. Although cleans-
ing products containing soaps, detergents, or
astringents can remove surface sebum, they do
not stop the F
ow of oil that contributes to acne.
Abrasive products are harmful because they irri-
tate the skin and increase inF
Most acne treatments take weeks to months to
work. Women with acne are sometimes prescribed
certain types of birth control pills because the
estrogens counter androgen excess. Isotretinoin is
a very e³
ective derivative of vitamin A but has side
ects and causes birth defects. Systemic antibiot-
ics can treat acne by clearing bacteria from seba-
ceous glands. Topical treatments include tretinoin
(another vitamin A derivative), salicylic acid (an
aspirin solution), and benzoyl peroxide.
Treatment for severe acne requires a doctor’s
care. Drug combinations are tailored to the sever-
ity of the condition (table 6A).
The regulation of body temperature is vitally important
because even slight shifts can disrupt the rates of metabolic
reactions. Normally, the temperature of deeper body parts
remains close to a set point of 37°C (98.6°F). The mainte-
nance of a stable temperature requires that the amount of
heat the body loses be balanced by the amount it produces.
The skin plays a key role in the homeostatic mechanism that
regulates body temperature.
To Chapter 1, Homeostasis, pages 9–10.
Heat Production and Loss
Heat is a product of cellular metabolism; thus, the more
active cells of the body are the major heat producers. These
the apocrine glands are most numerous in axillary regions,
the groin, and the area around the nipples. Ducts of these
glands open into hair follicles.
Other sweat glands are structurally and functionally
modi± ed to secrete speci± c fl
uids, such as the ceruminous
glands of the external ear canal that secrete ear wax (see
chapter 12, p. 450) and the female mammary glands that
secrete milk (see chapter 23, pp. 902–903).
Table 6.2
marizes skin glands.
How does the composition of a ±
ngernail di³
er from that of a hair?
Explain how a hair forms.
What causes gooseF
What is the function of the sebaceous glands?
Describe the locations of the sweat glands.
How do the functions of eccrine sweat glands and apocrine sweat
glands di³
Acne Treatments (by Increasing Severity)
ammatory comedonal acne (blackheads
and whiteheads)
Topical tretinoin or salicylic acid
Papular inF
ammatory acne
Topical antibiotic
Widespread blackheads and pustules
Topical tretinoin and systemic antibiotic
Severe cysts
Systemic isotretinoin
Explosive acne (ulcerated lesions, fever, joint pain)
Systemic corticosteroids
Acne is a common skin
condition usually associated with a surge of
androgen activity—not eating chocolate, as
was once believed.
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