Chapter 21: The Skin
Chapter Objectives
• Epidermis, dermis and subcutaneous
tissues.
• Roles of keratin and melanin in the
skin.
• The glands in the skin.
• The structure of hair and of nails.
• Roots pertaining to the skin.
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Key Terms
Normal Structure and Function
cutaneous
Pertaining to the skin (from Latin cutis, meaning “skin”)
derma
Skin (from Greek)
dermis
The layer of the skin between the epidermis and the
subcutaneous tissue; the true skin or corium
epidermis
The outermost layer of the skin (from epi-, meaning “upon or over”
and derm, meaning “skin”)
hair
A threadlike keratinized outgrowth from the skin (root: trich/o)
hair follicle
The sheath in which a hair develops
integumentary system
The skin and its associated glands, hair, and nails
keratin
A protein that thickens and toughens the skin and makes up hair
and nails (root: kerat/o)
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Key Terms
Normal Structure and Function (cont’d)
melanin
A dark pigment that gives color to the hair and skin and protects the
skin against the sun's radiation (root melan/o)
nail
A platelike keratinized outgrowth of the skin that covers the dorsal
surface of the terminal phalanges (root: onych/o)
sebaceous gland
A gland that produces sebum; usually associated with a hair follicle
(root: seb/o)
sebum
A fatty secretion of the sebaceous glands that lubricates the hair and
skin (root: seb/o)
skin
The tissue that covers the body; the integument (root: derm/o,
dermat/o)
subcutaneous tissue
The layer of tissue beneath the skin; also called the hypodermis
sudoriferous gland
A sweat gland (root: hidr/o)
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Key Terms
Disorders
atopic dermatitis
Hereditary, allergic, chronic inflammation of the skin with pruritus
(itching); eczema
basal cell
carcinoma
An epithelial tumor that rarely metastasizes and has a high cure rate
with surgical removal
cicatrization
The process of scar formation; a scar is a cicatrix (SIK-a-triks)
debridement
Removal of dead or damaged tissue, as from a wound
dehiscence
Splitting or bursting, as when the layers of a wound separate
dermatitis
Inflammation of the skin, often associated with redness and itching;
may be caused by allergy, irritants (contact dermatitis), or a variety of
diseases
dermatology
Study of the skin and diseases of the skin
dermatome
Instrument for cutting thin sections of skin for skin grafting
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Key Terms
Disorders (cont’d)
eczema
A general term for an inflammation of the skin with redness, lesions,
and itching; atopic dermatitis
erythema
Diffuse redness of the skin
escharotomy
Removal of scab tissue (eschar) resulting from burns or other skin
injuries
evisceration
Protrusion of internal organs (viscera) through an opening, as through
a wound
exudates
Material, which may include fluid, cells, pus, or blood, that escapes
from damaged tissue
Kaposi sarcoma
Cancerous lesion of the skin and other tissues seen most often in
patients with AIDS
keloid
A raised, thickened scar caused by tissue overgrowth during scar
formation
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Key Terms
Disorders (cont’d)
lupus
erythematosus (LE)
A chronic, inflammatory, autoimmune disease of connective tissue
that often involves the skin; types include the more widespread
systemic lupus erythematosus (SLE) and a discoid form (DLE) that
involves only the skin
malignant
melanoma
A metastasizing pigmented tumor of the skin
pemphigus
An autoimmune disease of the skin characterized by sudden,
intermittent formation of bullae (blisters); may be fatal if untreated
pressure ulcer
An ulcer caused by pressure to an area of the body, as from a bed or
chair; decubitus (dē-KŪ-bi-tus) ulcer, bedsore, pressure sore
pruritus
Severe itching
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Key Terms
Disorders (cont’d)
psoriasis
A chronic hereditary dermatitis with red lesions covered by silvery
scales
rule of nines
A method for estimating the extent of body-surface area involved in a
burn by assigning percentages in multiples of nine to various regions
of the body
scleroderma
A chronic disease that is characterized by thickening and tightening
of the skin and that often involves internal organs in a form called
progressive systemic sclerosis (PSS)
squamous cell
carcinoma
An epidermal cancer that may invade deeper tissues but tends not to
metastasize
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Supplementary Terms
Symptoms and Conditions
acne
An inflammatory disease of the sebaceous glands and hair follicles
usually associated with excess secretion of sebum; acne vulgaris
actinic
Pertaining to the effects of radiant energy, such as sunlight, ultraviolet
light, and x-rays
albinism
A hereditary lack of pigment in the skin, hair, and eyes
alopecia
Absence or loss of hair; baldness
beau lines
White lines across the fingernails; usually a sign of systemic disease
or injury
bromhidrosis
Sweat that has a foul odor because of bacterial decomposition; also
called bromidrosis
carbuncle
A localized infection of the skin and subcutaneous tissue, usually
caused by staphylococcus, and associated with pain and discharge of
pus
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Supplementary Terms
Symptoms and Conditions (cont’d)
comedo
A plug of sebum, often containing bacteria, in a hair follicle; a
blackhead (plural: comedones)
dermatophytosis
Fungal infection of the skin, especially between the toes; athlete's
foot (root: phyt/o means “plant”)
diaphoresis
Profuse sweating
dyskeratosis
Any abnormality in keratin formation in epithelial cells
ecchymosis
A collection of blood under the skin caused by leakage from small
vessels
erysipelas
An acute infectious disease of the skin with localized redness and
swelling and systemic symptoms
erythema nodosum
Inflammation of subcutaneous tissues resulting in tender,
erythematous nodules; may be an abnormal immune response to a
systemic disease, an infection, or a drug
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Supplementary Terms
Symptoms and Conditions (cont’d)
exanthema
Any eruption of the skin that accompanies a disease, such as measles;
a rash
excoriation
Lesion caused by scratching or abrasion
folliculitis
Inflammation of a hair follicle
furuncle
A painful skin nodule caused by staphylococci that enter through a hair
follicle; a boil
hemangioma
A benign tumor of blood vessels; in the skin, called birthmarks or port
wine stains
herpes simplex
A group of acute infections caused by herpes simplex virus. Type I
herpes simplex virus produces fluid-filled vesicles, usually on the lips,
after fever, sun exposure, injury, or stress; cold sore, fever blister. Type
II infections usually involve the genital organs.
hirsutism
Excessive growth of hair
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Supplementary Terms
Symptoms and Conditions (cont’d)
ichthyosis
A dry, scaly condition of the skin (from the root ichthy/o, meaning
“fish”)
impetigo
A bacterial skin infection with pustules that rupture and form crusts;
most commonly seen in children, usually on the face
keratosis
Any skin condition marked by thickened or horny growth. Seborrheic
keratosis is a benign tumor, yellow or light brown in color, that
appears in the elderly. Actinic keratosis is caused by exposure to
sunlight and may lead to squamous cell carcinoma.
lichenification
Thickened marks caused by chronic rubbing, as seen in atopic
dermatitis (a lichen is a flat, branching type of plant that grows on
rocks and bark)
mycosis fungoides
A rare malignant disease that originates in the skin and involves the
internal organs and lymph nodes. There are large, painful, ulcerating
tumors.
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Supplementary Terms
Symptoms and Conditions (cont’d)
nevus
A defined discoloration of the skin; a congenital vascular tumor of the
skin; a mole, birthmark
paronychia
Infection around a nail. Caused by bacteria or fungi, and may affect
multiple nails
pediculosis
Infestation with lice
petechiae
Flat, pinpoint, purplish-red spots caused by bleeding within the skin or
mucous membrane (singular, petechia)
photosensitization
Sensitization of the skin to light, usually from the action of drugs, plant
products, or other substances
purpura
A condition characterized by hemorrhages into the skin and other
tissues
rosacea
A condition of unknown cause involving redness of the skin, pustules,
and overactivity of sebaceous glands, mainly on the face
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Supplementary Terms
Symptoms and Conditions (cont’d)
scabies
A highly contagious skin disease caused by a mite
senile lentigines
Brown macules that appear on sun-exposed skin in adults; liver spots
shingles
An acute eruption of vesicles along the path of a nerve; herpes zoster
(HER-pēz ZOS-ter); caused by the same virus that causes
chickenpox
tinea
A fungal infection of the skin; ringworm
tinea versicolor
Superficial chronic fungal infection that causes varied pigmentation of
the skin
urticaria
A skin reaction marked by temporary, smooth, raised areas (wheals)
associated with itching; hives
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Supplementary Terms
Symptoms and Conditions (cont’d)
venous stasis ulcer
Ulcer caused by venous insufficiency and stasis of venous blood;
usually forms near the ankle
verruca
An epidermal tumor; a wart
vitiligo
Patchy disappearance of pigment in the skin; leukoderma
xeroderma
pigmentosum
A fatal hereditary disease that begins in childhood with discolorations
and ulcers of the skin and muscle atrophy. There is increased
sensitivity to the sun and increased susceptibility to cancer.
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Abbreviations
BSA
Body-surface area
DLE
Discoid lupus erythematosus
FTSG
Full-thickness skin graft
LE
Lupus erythematosus
PSS
Progressive systemic sclerosis
PUVA
Psoralen ultraviolet A
SCLE
Subacute cutaneous lupus erythematosus
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Abbreviations (cont’d)
SLE
Systemic lupus erythematosus
SPF
Sun protection factor
STSG
Split-thickness skin graft
UV
Ultraviolet
UVA
Ultraviolet A
UVB
Ultraviolet B
VAC
Vacuum-assisted closure
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Roots Pertaining to the Skin
Root
Meaning
Example
Definition of Example
derm/o,
dermat/o
skin
dermabrasion
surgical procedure used to resurface
the skin and remove imperfections
kerat/o
keratin, horny
layer of the skin
keratinous
containing keratin; horny
melan/o
dark, black,
melanin
melanosome
a small cellular body that produces
melanin
hidr/o
sweat,
perspiration
anhidrosis
absence of sweating
seb/o
sebum,
sebaceous gland
seborrhea
excess flow of sebum
trich/o
hair
trichomycosis
fungal infection of the hair
onych/o
nail
onychia
inflammation of the nail and nail bed
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Anatomy of the Skin
• Skin is part of integumentary system
• Epidermis = outermost layer
– 4-5 layers of epithelial cells
– Stratum basale
• Deepest layer of epidermis
• Produces new skin cells
• New skin cells gradually rise to surface
• As skin cells rise:
• Cells die
• Cells fill with keratin
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Anatomy of the Skin (cont’d)
– Stratum corneum = outermost layer of epidermis
• Flat, dead, protective cells
• Constantly shed and replaced
• Some cells produce melanin
• Gives color to skin
• Protects against sunlight
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Dermis & Subcutaneous Tissue
• Dermis = layer beneath epidermis
– Connective tissue
– Nerves
– Blood vessels
– Lymphatics
– Supports and nourishes skin
• Subcutaneous tissue = layer beneath dermis
– Connective tissue
– Fat
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Cross Section of the Skin
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Associated Skin Structures
• Sudoriferous glands (sweat glands)
– Regulate temperature
– Release watery fluid (sweat)
– Sweat evaporates cooling the body
• Sebaceous glands
– Release sebum (oily fluid)
– Lubricates hair and skin to prevent drying
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Associated Skin Structures (cont’d)
• Hair
– Nonliving material, mainly keratin
– Develops within follicle
– Grows from base within deep layers of skin
– Functions as protection
• Nails
– Nonliving material, mainly keratin
– Develops from growing region at proximal end
– Functions as protection
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Clinical Aspects of the Skin
• Dermatology = study of skin and skin diseases
• Observation of skin, hair, nails part of every physical
examination
– Skin observed for color, unusual pigmentation,
lesions
– Palpated to evaluate texture, temperature, moisture,
firmness, tenderness
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Wounds
• Caused by:
– Trauma
– Surgery
• Complicated by:
– Infection
– Hemorrhage
– Dehiscence = disruption of wound layers
– Evisceration = protrusion of internal organs through lesion
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Wound Healing
• As wound heals:
– Fluid and cells drain from damaged tissue
– Exudate may be:
• Clear
• Bloody
• Pus-containing
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Wound Healing (cont’d)
• Proper wound healing:
– Cleanliness and care of lesion
– Proper circulation
– Good general health and nutrition
– Accompanied by cicatrization (scar formation)
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Promotion of Healing
• Vacuum-assisted closure = negative pressure to close
tissues
• Debridement = removal of dead or damaged tissue
– Cutting or scrubbing
– Enzymes
– Escharotomy (removal of scar)
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Promotion of Healing (cont’d)
• Skin graft
– For deep wounds
– Full thickness skin graft (FTSG)
• Epidermis and dermis
– Split-thickness skin graft (STSG)
• Epidermis
– Done with dermatome
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Burns
• Caused by:
–
Hot objects
–
Explosions
–
Scalding
–
Electrical malfunctions
–
Contact with harmful chemicals
–
Abrasion
• Assessed by:
–
Depth of damage
–
Percentage of body surface area affected
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Burn Categorization
• Superficial partial thickness
– Involves epidermis, possibly dermis
– Tissue reddens, may blister
• Deep partial-thickness
– Involves epidermis and portions of dermis
– Tissue blisters, has weeping surface
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Burn Categorization (cont’d)
• Full-thickness
– Involves full skin, possibly subcutaneous tissue
– Broken, dry and pale or charred tissue
– May result in loss of digits or limbs
– May require skin grafting
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Burn Categorization (cont’d)
• Percentage of body surface area
– Rule of nines
• Areas of body surface assigned percentages in
multiples of nine
– Lund and Browder
• More accurate
• Divides body into small areas
• Estimates proportion each area contributes
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Burn Treatment
• Includes:
– Respiratory care
– Administration of fluids
– Wound care
– Pain control
– Monitoring for complications
• Infections
• Cardiovascular
• Respiratory
– Posttraumatic stress
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Pressure Ulcers
• Necrotic skin lesions
• Body resting on skin covering bony projections
– Sacrum
– Heel
– Elbow
– Ischial bone of pelvis
– Greater trochanter of femur
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Pressure Ulcers (cont’d)
• Interrupts circulation
–
Thrombosis
–
Ulceration
–
Death of tissue
• Contributing factors:
–
Malnutrition
–
Age
–
Obesity
–
Infection
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Pressure Ulcers (cont’d)
• Progression
– First appear as redness of skin
– If ignored may penetrate:
• Skin
• Underlying muscle
• Bone
– May require months to heal
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Pressure Ulcers (cont’d)
• Prevention
– Pads or mattresses to relieve pressure
– Regular cleansing and drying of skin
– Frequent change in position
– Good nutrition
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Dermatitis
• Inflammation of skin
• Example: Eczema (atopic dermatitis)
– Chronic allergic form
– Exact cause unknown, but made worse by:
• Allergies
• Infection
• Temperature extremes
• Skin irritants
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Dermatitis (cont’d)
• Other forms:
– Contact dermatitis
– Seborrheic dermatitis
– Stasis dermatitis
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Psoriasis
• Chronic overgrowth of epidermis
• Large erythematous plaques with silvery scales
• Cause unknown, but may be linked with:
–
Hereditary pattern
–
Autoimmunity
• Treatment
–
Topical corticosteroids
–
Exposure to UV light
–
Systemic suppression of immune system
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Autoimmune Disorders
• Pemphigus
– Characterized by formation of blisters
• Occurs in skin and mucous membranes
• Caused by separation of epidermal cells from
underlying layers
– Deep skin unprotected from infection and fluid loss
– Caused by autoimmune reaction
– Fatal unless immune system is suppressed
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Autoimmune Disorders (cont’d)
• Lupus Erythematosus
– Chronic inflammatory autoimmune disease of connective
tissue
• Discoid
• Involves only the skin
• Systemic lupus erythematosus
• Involves skin and other organs
– Symptoms
• Rough, raised, violet-tinted papules
• Worsened by exposure to UV rays
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Scleroderma
• Thickening and tightening of skin
• Unknown cause
• Overproduction of collagen
• Involves hair follicles and sweat glands
• Early signs:
– Raynaud disease
– Skin symptoms first appear on forehead, around
mouth
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Skin Cancer
• Most common type of human cancer
• Increasing rate due UV rays
• Common types
– Squamous cell carcinoma
– Basal cell carcinoma
– Malignant melanoma
– Kaposi sarcoma
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Skin Cancer (cont’d)
• Squamous cell carcinoma
– Cancer of epithelial cell
• Occurs in areas exposed to sunlight
• Painless, firm red nodule
• May invade underlying tissue
• Tends not to metastasize
• Treatment
• Surgical removal
• X-irradiation
• Chemotherapy
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Skin Cancer (cont’d)
• Basal cell carcinoma
– 75% of all skin cancers
– Cancer of epithelial cell
• Occurs in areas exposed to sunlight
• Smooth, pearly papule
• After excision, cure rate 95%
• Easily seen
• Tends not to metastasize
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Skin Cancer (cont’d)
• Malignant melanoma
– Overgrowth of melanocytes
– Metastasizing tendency
– First appears as lesion
– May spread superficially before invading deeper tissues
– Prognosis good if lesion removed before reaching deeper
tissues
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Skin Cancer (cont’d)
• Kaposi Sarcoma
– Frequently associated with AIDS
– Distinct brownish area on legs
– As tumor progresses:
• Plaques become raised and firm
– Cancer can metastasize
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Pretest
1. The uppermost portion of the skin is called the:
(a) fossa
(b) cuticle
(c) epidermis
(d) epiphysis
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Pretest
1. The uppermost portion of the skin is called the:
(a) fossa
(b) cuticle
(c) epidermis
(d) epiphysis
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Pretest
2. A hair grows within a sheath called the:
(a) follicle
(b) hyaline
(c) fascia
(d) vesicle
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Pretest
2. A hair grows within a sheath called the:
(a) follicle
(b) hyaline
(c) fascia
(d) vesicle
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Pretest
3. The glands that secrete an oily substance that lubricates
the skin are the:
(a) sweat glands
(b) sebaceous glands
(c) mammary glands
(d) foramina
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Pretest
3. The glands that secrete an oily substance that lubricates
the skin are the:
(a) sweat glands
(b) sebaceous glands
(c) mammary glands
(d) foramina
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Pretest
4. The rule of nines is a system used to evaluate:
(a) burns
(b) fever
(c) inflammation
(d) immunity
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Pretest
4. The rule of nines is a system used to evaluate:
(a) burns
(b) fever
(c) inflammation
(d) immunity
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Pretest
5. A pigmented skin tumor is a(n):
(a) chondrosarcoma
(b) melanoma
(c) lymphoma
(d) adenoma
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Pretest
5. A pigmented skin tumor is a(n):
(a) chondrosarcoma
(b) melanoma
(c) lymphoma
(d) adenoma
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Pretest
6. The root hidr/o pertains to:
(a) tears
(b) saliva
(c) blood
(d) sweat
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Pretest
6. The root hidr/o pertains to:
(a) tears
(b) saliva
(c) blood
(d) sweat
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Pretest
7. Onychomycosis is a fungal infection of a(n):
(a) eyelid
(b) nail
(c) hair
(d) bone
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Pretest
7. Onychomycosis is a fungal infection of a(n):
(a) eyelid
(b) nail
(c) hair
(d) bone
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