Chapter 26
The Integumentary System
The Skin
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Functions of the Skin
• Protection
– Against invasion by bacteria
– Underlying tissue from injury
– Against loss of body fluid
• Perception
– Works with the nervous system to provide a
sense of touch
– Registers pain, heat, cold, and pressure
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Functions of the Skin
• Absorption
– Skin can absorb moisture and medication as well
as some vital vitamins and minerals through the
hair follicles and glands.
– Vitamin E is lipid-soluble and can pass through
the skin
• Excretion
– Skin eliminates water, salt, and waste.
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Functions of the Skin
• Temperature control
– When the temperature control center in the brain
senses that the body is too warm, blood vessels
dilate so that heat escapes through the skin
surface.
– When it is cold, the vessels constrict to prevent
heat loss from the skin surface.
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Structures of the Skin
• In 1 square centimeter of skin, there are:
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3 million cells
24 sensory apparatuses for heat and cold
200 nerve endings
25 pressure apparatuses
4 yards of nerves
3,000 sensory cells
700 sweat glands
1 yard of blood vessels
15 sebaceous glands
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How the Body Cools Its Surface
• The skin contains sweat glands that produces
moisture when the body is too hot.
• This moisture evaporates from the skin
surface to provide a cooling effect.
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The Three Layers of Skin Tissue
Epidermis
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Top layer
Dermis
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Middle layer
Filled with fat, blood vessels,
sweat and oil glands, and
nerves
Subcutaneous
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Inner layer
Contains blood vessels,
nerves, and hair follicles
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4 Appendages of the Skin
Sweat glands
– Produce moisture to cool the skin surface
Oils glands
– Produce oils to prevent hair and skin from
becoming dry and brittle
– Located in or near hair follicles over the entire
surface except your palms and soles
Hair
Nails
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The Process That Causes Wrinkles
• With age, the elastic fiber in the dermis increases in
size, and collagen in the dermis degenerates.
• The support for the epidermis is decreased and
wrinkles develop.
• Treatment involves controlled scraping of the top
layers of skin is called dermabrasion
• A medium peel would affect medium surface and
some underlying cells
• Excoriation is a scrape or burn
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What Causes a Suntan to Develop
• When the skin is exposed to the sun, it may
become reddened because of superficial
blood vessel dilation.
• The melanin pigment increases and moves to
the surface to protect the underlying tissue.
• A brownish coloration or suntan appears.
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Basal Cell Carcinoma
• Slow-growing, locally destructive skin tumor;
also called skin cancer
• Usually occurs in areas where there are
abundant sebaceous follicles
• More common in persons over 40, especially
those who are blond and fair skinned
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Squamous Cell Carcinoma
• Invasive tumor that has metastatic potential
• Usually occurs in Caucasian men over the age
of 60
• Working outdoors and smoking increases the
risk for developing this cancer.
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Ordinary Moles versus Melanoma
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Shape
Border
Color
Diameter
Development
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Factors that Contribute to the
Development of Melanoma
• Intense exposure to ultraviolet (UV) rays from
sunlight
• Blond or red hair
• Fair skin with tendency to sunburn
• Blue eyes
• An asymmetrical melanoma may have shades
of red, white or blue
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Blushing
• The skin has a rich supply of blood vessels.
• When we blush, the vessels dilate and cause
reddening of the skin.
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Birthmarks and Moles
• Birthmarks can be caused by coloration from a
collection of blood vessels or from patches of
skin pigment.
• Moles are pigmented patches of skin.
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Albinism
• Persons who have little or no skin pigment to
give it color are identified as albinos.
• The hair is pale yellow or white.
• The eyes appear red and are very sensitive to
light.
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Alopecia
• Loss of hair that usually occurs in the scalp
• Physiologic alopecia
– Temporary hair loss
• Alopecia areata
– Limited to small patches of hair loss
• Male pattern baldness
– Most common form of hair loss
– Affects men over age 30
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Cellulitis
• Acute diffuse or spreading inflammation of
the skin and subcutaneous tissue
• Causes localized swelling, pain, heat, and
redness
• Usually the result of a streptococcus or
Staphylococcus infection
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Eczema
• Acute or chronic skin disorder that results in
dry, red, itchy, and scaly skin
• Eczema can be irritated by diet, cosmetics,
clothing, medications, soaps, and
environmental elements, as well as emotional
stress.
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Dermatitis and Folliculitis
• Dermatitis
– Inflammation of the skin
– Can refer to any form of skin condition such as
seborrhea, eczema, contact dermatitis,
exfoliative dermatitis, or stasis
• Folliculitis
– Infection of the hair follicle with the formation of
a pustule
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Furuncles and Carbuncles
• Furuncles
– Hard, painful nodules that develop over time and
then rupture and release pus and dead cells
through a drainage point
– May develop from folliculitis
• Carbuncles
– Began as a nodule, then enlarge and have multiple
drainage points
– Treated with systemic antibiotics
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Herpes
• Viral infection that causes groups of small,
painful, clear vesicles
• Type I: Lesions appear in the mouth and nasal
area.
• Type II: Lesions appear in the genitals.
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Herpes Zoster
• Also called shingles
• Acute infectious process from the same virus
that causes chickenpox
• Results in fever, malaise, and usually unilateral
eruption of vesicles on the back, chest, or
neck
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Hirsutism and Impetigo
• Hirsutism
– Excessive development of body hair that could be
hereditary or the result of an endocrine system
disorder
• Impetigo
– Contagious skin infection with macules and
vesicles that erupt and form a characteristic
yellow crust
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Keloids and Lyme Disease
• Keloids
– Scars that develop excess dense tissue as they
heal
• Lyme disease
– Tick-borne disease that is generally the result of a
spirochete-infested deer tick
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Pediculosis
• The infestation of parasitic lice
• Pediculosis capitis
– Head lice
• Pediculosis corpus
– Body lice
• Pediculosis pubis
– Lice attached to pubic hair; commonly called crabs
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Poison Ivy and Psoriasis
• Poison ivy
– Dermatitis that results from contact with the
poison ivy plant
• Psoriasis
– Chronic inflammatory skin condition that causes
red papules covered with silvery scales
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Rosacea and Ringworm
• Rosacea
– Chronic skin eruption that makes the face,
especially the nose and cheeks, look flushed
• Ringworm
– Fungal infection that causes flat lesions that may
be dry and scaly or moist and crusty
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Scabies and Urticaria
• Scabies
– Skin infection caused by a skin mite; results in
intense itching
• Urticaria
– Also called hives; a self-limiting reaction to
allergens that results in distinct wheals
surrounded by reddened areas
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Verrucae & Vesicles
• Also called warts; a benign viral infection of
the skin that results in rough, elevated,
rounded areas on the skin surfaces
• Vesicles are lesions that may be caused by
chicken pox
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Need to know definitions of:
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Subcutaneous
Ulcer
Fissure
Transdermal
Wheal
Epidermis
Erythema
Constrict
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Melanin
Pustule
Basal cell carcinoma
Dermis
Pediculosis pubis
Carotene
Squamous cell carcinoma
Dermatitis
Pediculosis capitis
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