C om parison o f a m ole and a m alig n an t m elanom a • Figure 4.11
Malignant melanomas are the most aggressive form of skin cancer.
ABCDE warning signs of malignant melanoma (MM)
A
asymmetry - MMs lack symmetry
B border - MMs have irregular borders
C
color - MMs have uneven coloration and may contain
many colors
D diameter - MMs are larger than ordinary moles (>5 mm)
E evolving - MMs change in size, shape, or color
Risk factors include skin type (light =high risk), sun
exposure (number of severe sunburns), family history of
cancer, age, and immune status (immunosuppressed =
high risk).
b.
Malignant melanoma
Malignant melanoma (2% of all skin cancers)—Tumors
arise from melanocytes, metastasize quickly, and can
kill a patient within months of diagnosis (Figure 4.11).
The best way to prevent skin cancer is to reduce expo-
sure to UV radiation from the sun or tanning beds. Tightly
woven clothes keep the sun’s rays out, and hats prevent
the scalp from being exposed. Sunscreen lotions reduce
the damaging effects of UV radiation. They should be con-
sistently applied while outside and reapplied after swim-
ming. Sunscreens are rated by their sun protection factor
(SPF). SPF numbers refer to the amount of time it would
take to burn if an individual were wearing sunscreen com-
pared to not wearing sunscreen. Everyone should use sun-
screen with a minimum SPF of 15. The fairer your skin,
the higher the SPF should be: Fair-skinned individuals
should probably apply sunscreen with an SPF of 55.
CONCEPT CHECK
1.
How
do skin wrinkles develop with age?
2.
What
is the most dangerous form of skin cancer?
THE PLANNER
Summary
I
The Integumentary System Is Composed of
Skin, Glands, Hair, Nails, and Nerve Endings 92
• The integumentary system consists of the skin, hair, oil
glands, sweat glands, and nails. The principal parts of the skin,
as shown, are the superficial epidermis and deeper dermis,
which overlies and is attached to the subcutaneous layer.
• The epidermis is composed of four or five layers containing
many cells with various functions. Keratinocytes, the most
common cells of the epidermis, produce the intracellular
protein keratin. Other cells give color to the skin (mela-
nocytes), participate in immunity (Langerhans cells), and
provide cutaneous sensations (Merkel cells). •
• The dermis consists of dense irregular connective tissue with
collagen and elastic fibers. The papillary region contains thin
collagen and fine elastic fibers. The reticular region contains
thick collagen fibers, adipose tissue, hair follicles, nerves, oil
glands, and sweat glands.
106
CHAPTER 4
The Integumentary System
EPIDERMIS
DERMIS
Subcutaneous
layer
The skin • Figure 4.1a
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