Chapter 6
The Integumentary System and Body
Membranes
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Objectives
• Classify, compare the structure of, and give examples of
each type of body membrane
• Describe the structure and function of the epidermis and
dermis
• List and briefly describe each accessory organ of the
skin
• List and discuss the three primary functions of the
integumentary system
• List and describe major skin disorders and infections
• Classify burns and describe how to estimate the extent
of a burn injury
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Classification of
Body Membranes
• Classification of body membranes
– Epithelial membranes—composed of
epithelial tissue and an underlying layer of
connective tissue
– Connective tissue membranes—composed
exclusively of various types of connective
tissue
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Classification of
Body Membranes
• Epithelial membranes
– Cutaneous membrane—the skin
– Serous membranes—simple squamous
epithelium on a connective tissue
basement membrane
• Parietal—line walls of body cavities
• Visceral—cover organs found in body cavities
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Classification of
Body Membranes
• Examples
– Pleura—parietal and visceral layers line
walls of thoracic cavity and cover the lungs
– Peritoneum—parietal and visceral layers
line walls of abdominal cavity and cover
the organs in that cavity
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Classification of
Body Membranes
• Diseases
– Pleurisy—inflammation of the serous
membranes that line the chest cavity and
cover the lungs
– Peritonitis—inflammation of the serous
membranes in the abdominal cavity that
line the walls and cover the abdominal
organs
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Classification of
Body Membranes
• Mucous membranes
– Line body surfaces that open directly to the
exterior
– Produce mucus, a thick secretion that
keeps the membranes soft and moist
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Classification of
Body Membranes
• Connective tissue membranes
– Do not contain epithelial components
– Produce a lubricant called synovial fluid
– Examples
• The synovial membranes in the spaces
between joints and in the lining of the bursal
sacs
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The Skin
• Structure—two primary layers called
epidermis and dermis
– Epidermis
• Outermost and thinnest primary layer of skin
• Composed of several layers of stratified
squamous epithelium
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The Skin
• Structure
– Epidermis
• Stratum germinativum—innermost (deepest) layer of cells
that continually reproduce; new cells move toward the
surface
– Sometimes called the pigment layer
– Pigment cells called melanocytes, which produce the brown
pigment melanin
• As cells approach the surface, they are filled with a tough,
waterproof protein called keratin and eventually flake off
• Stratum corneum—outermost layer of keratin-filled cells
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The Skin
• Structure
– Epidermis
• Skin color changes
– Pink flush indicates increased blood volume or increased
blood oxygen
– Cyanosis—bluish gray color indicates decreased blood
oxygen level
– Vitiligo—patchy light skin areas resulting from acquired
loss of epidermal melanocytes (Figure 6-4)
– Increased skin pigmentation caused by hormonal changes
in pregnant women
– Freckles—small, flat macules—common normal skin
pigment variation
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The Skin
• Dermal-epidermal junction—specialized
area of contact between the epidermis
and dermis; sometimes described as
“spot welds”
– Provide support for epidermis
– Weakened or destroyed junctions can
cause blisters
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The Skin
• Structure
– Dermis
• Deeper and thicker of the two primary skin layers and
composed largely of connective tissue
• Upper area of dermis characterized by parallel rows of
peglike dermal papillae
• Thick skin has parallel friction ridges and no hairs
• Thin skin has irregular, shallow grooves and hair
• Deeper area of dermis is filled with network of tough
collagenous and stretchable elastic fibers
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The Skin
• Structure
– Dermis
• Number of elastic fibers decreases with age
and contributes to wrinkle formation
– Striae—“stretch marks”; elongated marks caused by
overstretching of skin
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The Skin
• Structure
– Dermis
• Dermis also contains nerve endings, muscle
fibers, hair follicles, sweat and sebaceous
glands, and many blood vessels
– Birthmarks—malformation of dermal blood vessels
» Strawberry hemangioma
» Port-wine stain
» Stork bite
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The Skin
• Appendages of the skin
– Hair
• Soft hair of fetus and newborn called lanugo
• Hair growth requires epidermal tubelike
structure called hair follicle
• Hair growth begins from hair papilla
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The Skin
• Appendages of the skin
– Hair
• Hair root lies hidden in follicle; visible part of
hair called shaft
• Alopecia (Figure 6-8)—hair loss
• Arrector pili—specialized smooth muscle that
produces “goose pimples” and causes hair to
stand up straight
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The Skin
• Appendages of the skin
– Receptors
• Specialized nerve endings—make it possible
for skin to act as a sense organ
– Meissner (tactile) corpuscle—capable of detecting
light touch
– Lamellar (Pacini) corpuscle—capable of detecting
pressure
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The Skin
• Nails
– Produced by epidermal cells over terminal ends of
fingers and toes
– Visible part called nail body
– Root lies in a groove and is hidden by cuticle
– Crescent-shaped area nearest root called lunula
– Nail bed may change color with change in blood
flow
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The Skin
• Nails
– Normal variations in nail structure
• Longitudinal ridges in light-skinned individuals
• Pigmented bands in dark-skinned individuals
– Abnormal variations in nail structure
• Onycholysis—separation of nail from nail bed
• Pitting—common in psoriasis
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The Skin
• Skin glands—two main types
– Sweat, or sudoriferous
– Sebaceous
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The Skin
• Skin glands
– Sweat, or sudoriferous, glands
• Eccrine sweat gland
– Most numerous, important, and widespread of the
sweat glands
– Produce perspiration or sweat, which flows out
through pores on skin surface
– Function throughout life and assist in body heat
regulation
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The Skin
• Skin glands
– Sweat or sudoriferous glands
• Apocrine sweat glands
– Found primarily in axilla and around genitalia
– Secrete a thicker, milky secretion quite different from
eccrine perspiration
– Breakdown of secretion by skin bacteria produces
odor
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The Skin
• Skin glands
– Sebaceous glands
–
–
–
–
Secrete oil or sebum for hair and skin
Secretion increases during adolescence
Amount of secretion regulated by sex hormones
Sebum in sebaceous gland ducts may darken to
form a blackhead
– Acne vulgaris—inflammation of sebaceous gland
ducts
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Functions of the Skin
• Protection—first line of defense
–
–
–
–
–
Against infection by microbes
Against ultraviolet rays from sun
Against harmful chemicals
Against cuts and tears
Bruising can cause discoloration as blood
released from damaged vessels breaks down
– Skin grafts may be needed to replace skin
destroyed by disease or trauma
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Functions of the Skin
• Temperature regulation
– Skin can release almost 3000 calories of
body heat per day
– Mechanisms of temperature regulation
• Regulation of sweat secretion
• Regulation of flow of blood close to the body
surface
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Functions of the Skin
• Sense organ activity
– Receptors serve as receivers for the body,
keeping it informed of changes in its
environment
– Skin can detect sensations of light touch,
pressure, pain, heat, and color
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Disorders of the Skin
(Dermatoses)
• Skin lesions—any measurable variation from
the normal structure
– Elevated lesions—cast a shadow outside their
edges
•
•
•
•
•
•
Papule—small, firm raised lesion
Plaque—large raised lesion
Vesicle—blister
Pustule—pus-filled lesion
Crust—scab
Wheal (hive)—raised, firm lesion with a light center
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Disorders of the Skin
(Dermatoses)
– Flat lesions—do not cast a shadow
• Macule—flat, discolored region
– Depressed lesions cast a shadow within their
edges
• Excoriation—missing epidermis, as in a scratch
• Ulcer—craterlike lesion
• Fissure—deep crack or break
– Some lesions are produced by scrapes and
cuts—the skin can repair itself
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Burns
• Treatment and recovery or survival
depend on total area involved and
severity or depth of the burn
• Classification of burns
– First-degree (partial-thickness) burns—only
surface layers of epidermis involved
– Second-degree (partial-thickness) burns—
involve deep epidermal layers; always
cause injury to upper layers of the dermis
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Burns
• Classification of burns
– Third-degree (full-thickness) burns—
characterized by complete destruction of
the epidermis and dermis
• May involve underlying muscle and bone
(fourth degree)
• Lesion is insensitive to pain because of
destruction of nerve endings immediately after
injury—intense pain is experienced soon
thereafter
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Burns
• Estimating body surface area using the
“rule of nines” in adults
– Body divided into 11 areas of 9% each
– Additional 1% of body surface area around
genitals
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Skin Infections
• Impetigo—highly contagious staphylococcal
or streptococcal infection
• Tinea—fungal infection (mycosis) of the skin;
several forms occur
• Warts—benign neoplasm caused by
papillomavirus
• Boils—furuncles; staphylococcal infection in
hair follicles
• Scabies—parasitic infection
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Vascular and
Inflammatory Skin Disorders
• Decubitus ulcers (bedsores) develop when
pressure slows down blood flow to local
areas of the skin
• Urticaria or hives—red lesions caused by fluid
loss from blood vessels
• Scleroderma—disorder of vessels and
connective tissue characterized by hardening
of the skin; two types: localized and systemic
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Vascular and
Inflammatory Skin Disorders
• Psoriasis—chronic inflammatory
condition accompanied by scaly
plaques
• Eczema—common inflammatory
condition characterized by papules,
vesicles, and crusts; not a disease itself
but a symptom of an underlying
condition
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Skin Cancer
• Three common types
– Squamous cell carcinoma—the most
common type, characterized by hard,
raised tumors
– Basal cell carcinoma—characterized by
papules with a central crater; rarely
spreads
– Melanoma—malignancy in a nevus (mole);
the most serious type
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Skin Cancer
• The most important causative factor in
common skin cancers is exposure to
sunlight
• Kaposi sarcoma, characterized by
purple lesions, is associated with AIDS
and other immune deficiencies
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