• Burns can be extensive injuries. First-degree burns involve
only the epidermis and are characterized by redness and
mild pain. Second-degree burns involve both the epidermis
and dermis and are characterized by pain and blistering.
Third-degree burns involve extensive damage to epidermis,
dermis, and subcutaneous tissues. Fourth-degree burns
damage additional soft tissue underlying the skin, such as
muscle and tendons. Severely burned patients are suscep-
tible to circulatory shock and infection and may require skin
grafting to repair the lost tissue. The extent of burns on the
body is assessed using the rule of nines.
^ 4 Aging and Skin Cancer 105
• Age-related changes in the skin begin around age 40. The
protein fibers in the dermis become stiff and brittle and be-
gin to break down. Most skin cells decrease in number and
do not lay down new protein fibers as quickly. The secre-
tions of oil (sebaceous) and sweat (sudoriferous) glands are
reduced. Melanocytes decrease in number and stop produc-
ing melanin. These changes lead to wrinkled, dry skin, dot-
ted with age spots. In addition, the skin is easily damaged
and is slow to heal. Hair loss begins around age 30.
• Prolonged exposure to UV radiation from the sun or tanning
beds over a lifetime has cumulative effects on the skin. UV
rays can depress the immune system, cause sunburn, and
damage the protein fibers in the dermis, and contribute to
the development of skin cancer.
• Skin cancer manifests itself in three forms: basal cell car-
cinoma (most common), squamous cell carcinoma (less
common), and malignant melanoma (the rarest but also
the deadliest). Malignant melanomas, as shown, arise from
melanocytes and metastasize quickly.
Malignant melanoma • Figure 4.11b
Key Terms
• albinism 95
• albino 95
• androgenic alopecia 97
• androgen 97
• apoptosis 94
• areolar connective tissue 93
• arrector pili 96
• axillary 97
• basal cell carcinoma 105
• bulb 96
• carotene 96
• ceruminous gland 98
• cutaneous membrane 93
• dermal papilla 95
• dermatology 92
• dermis 93
• edema 102
• epidermis 93
• hair 96
• hair follicle 96
• hair matrix 96
• hair root plexus 96
• hemoglobin 95
• hirsutism 97
• integumentary system 92
• keratin 94
• keratinization 95
• lunula 99
• male-pattern baldness 97
• malignant melanoma 106
• Meissner corpuscle 102
• melanin 95
• metastasize 105
• nail 99
• nevus 95
• nociceptors 102
• Pacinian corpuscle 102
• papilla of the hair 96
• pili 96
• root 96
• sebaceous gland 98
• shaft 96
• skin 93
• squamous cell carcinoma 105
• stem cell 94
• stratum basale 94
• stratum corneum 94
• stratum granulosum 94
• stratum lucidum 94
• stratum spinosum 94
• subcutaneous (subQ) layer 93
• sudoriferous gland 98
• thick skin 94
• thin skin 94
• vasodilation 97
• vitiligo 95
108
CHAPTER 4
The Integumentary System
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