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The Integumentary System Cheat Sheet by

Skin, hair, nails, associated glands, dermatology

Structure of the Skin & Subcut­aneous Tissue


Integu­mentary System
Consists of the skin, hair, nails, and associated glands
Scientific study and medical treatment of the integu­mentary system

Func­tions of the Skin

Resistance to trauma and infection
Keratin - Acid mantle
Other barrier functions
Waterp­roo­fing, UV radiation, Harmful chemicals
Vitamin D synthesis
Skin first step, Liver and kidneys complete process
Skin is our most extensive sense organ
Thermo­rec­eptors, Vasoco­nst­ric­tio­n/v­aso­dil­ation
Nonverbal commun­ication
Acne, birthmark, or scar
Transd­ermal absorption
Admini­str­ation of certain drugs steadily through thin skin via adhesive patches
Kerati­nized stratified squamous epithelium
-Dead cells at the surface packed with tough protein called keratin
-Lacks blood vessels
-Depends on the diffusion of nutrients from underlying connective tissue
-Sparse nerve endings for touch and pain

Sweat Glands

Two kinds of sweat (sudor­ife­rous) glands, Merocrine (eccrine) sweat glands
Apocrine sweat glands - Develop at puberty
• Bromhi­dro­sis­—di­sag­reeable body odor produced by bacterial action on fatty acids
• Diapho­res­is—­swe­ating with wetness of the skin
• Sebum—oily secretion produced by sebaceous glands
CERUMINOUS GLANDS - only in external ear canal
MAMMARY GLANDS —milk-­pro­ducing glands that develop only during pregnancy and lactation


Melanin—most signif­icant factor in skin color
-Produced by melano­cytes released by exocytosis
-Accumulate in the kerati­nocytes
-Eumelanin—brownish black
-Pheomelanin—a reddish yellow sulfur­-co­nta­ining pigment
-People of different skin colors have the same number of melano­cytes
Dark-s­kinned people
-Produce greater quantities of melanin
-Melanin granules in kerati­nocytes more spread out than tightly clumped
-Melanin breaks down more slowly
-Melanized cells seen throughout the epidermis
Light-­skinned people
-Melanin clumped near kerati­nocyte nucleus
-Melanin breaks down more rapidly
-Little seen beyond stratum basale
-Amount of melanin also varies with exposure to (UV) rays of sunlight
Hemoglobin—red pigment of red blood cells - Adds reddish to pinkish hue to skin
Carotene—yellow pigment acquired from egg yolks and yellow­/orange vegetables will turn skin yellow if consumed in large quanti­ties. - Concen­trates in stratum corneum and subcut­aneous fat


–leading cause of accidental death
Debrid­ement: removal of eschar (burned tissue)
–Classified according to the depth of tissue involv­ement
First-­degree burn: partia­l-t­hic­kness burn; involves only the epidermis
•Marked by redness, slight edema, and pain
Second­-degree burn: partia­l-t­hic­kness burn; involves the epidermis and part of the dermis
Third-­degree burn: full-t­hic­kness burn; the epidermis and all of the dermis, and often some deeper tissues (muscles or bones) are destroyed
•Often requires skin grafts
•Needs fluid replac­ement and infection control


-The body’s largest and heaviest organ
–Covers area of 1.5 to 2.0 m2
–15% of body weight
–Most skin is 1 to 2 mm thick
Two Layers: Epidermis & Dermis
Dermis­—co­nne­ctive tissue layer beneath the epidermis
–Ranges from 0.2 mm (eyelids) to 4 mm (palms, soles)
–Composed mainly of collagen with elastic fibers, reticular fibers, and fibrob­lasts
–Well supplied with blood vessels, sweat glands, sebaceous glands, and nerve endings
Hypodermis—another connective tissue layer below the dermis
Subcut­aneous tissue
–More areolar and adipose than dermis
–Pads body
–Binds skin to underlying tissues
Thick skin— on palms and sole, and corres­ponding surfaces on fingers and toes - Has sweat glands, but no hair follicles or sebaceous (oil) glands - Epidermis 0.5 mm thick
Thin Skin- covers rest of the body - Epidermis about 0.1 mm thick - Possesses hair follicles, sebaceous glands, and sweat glands

Five Types of Cells of the Epider­mis

Stem Cells
Undiff­ere­ntiated cells that give rise to kerati­nocytes
In deepest layer of epidermis (stratum basale)
Majority of epidermal cells
Synthesize keratin
very tough protein
Occur only in Stratum Basale
Synthesize pigment melanin that shields DNA from ultrav­iolet radiation
melanin accumu­lates in the kerati­nocytes
Tactile Cells
receptors for touch
Dendritic Cells
Macrophage (modified white blood cell)
originating in bone marrow that guard against pathogens
Guard against toxins, microbes, and other pathogens that penetrate skin

The Life History of a Kerati­noc­yte

Kerati­nocytes produced deep in the epidermis by stem cells in stratum Basale
Mitosis requires an abundant supply of oxygen and nutrients
Deep cells acquire oxygen from blood vessels in nearby dermis
Newly formed kerati­nocytes push the older ones toward the surface
-In 30 to 40 days a kerati­nocyte makes its way to the skin surface and flakes off
-Slower in old age - Faster in injured or stressed skin
Callus­es­\corns—thick accumu­lations of dead kerati­nocytes on the hands or feet
Waterp­roofing is Achieved By:
-Lipids secreted by kerati­nocytes
-Tight junctions between kerati­noc­ytes- thick layer of insoluble protein on the inner surfaces of the kerati­nocyte plasma membranes
-Critical to retaining water in the body and preventing dehydr­ation
Cells above the water barrier quickly die
-Barrier cuts them off from nutrients below
-Dead cells exfoliate (dander)
Dandruff: clumps of dander stuck together by sebum (oil)

Colors of Diagnostic Value

blueness of the skin
abnormal redness of the skin
pale or ashen color
genetic lack of melanin that results in white hair, pale skin, and pink eyes - Have inherited recessive, nonfun­ctional tyrosinase allele
yellowing of skin
Hematoma (Bruise)
mass of clotted blood showing through skin

Structure of Hair

Hair & Nails

Hair/nails are made of mostly dead, kerati­nized cells
-Pliable soft keratin makes up stratum corneum of skin
-Compact hard keratin makes up hair and nails
-Tougher and more compact due to numerous cross-­lin­kages between keratin molecules

Hair: Pilus

• Pilus— Hair —a slender filament of kerati­nized cells that grows from an oblique tube in the skin called a hair follicle
• Three kinds of hair grow over the course of our lives
fine, downy, unpigm­ented hair that appears on the fetus in the last 3 months of develo­pment not all infants are born with lanugo
fine, pale hair that replaces lanugo by time of birth
longer, coarser, and usually more heavily pigmented
Hair is divisible into three zones along its length
a swelling at the base where hair originates in dermis or hypodermis - Only living hair cells are in or near bulb
the remainder of the hair in the follicle
the portion above the skin surface
• Hair receptors – goosebumps - Piloer­ector muscle (arrector pili)
– Extends from dermal collagen to connective tissue root sheath Hair Texture and Color
• Textur­e—r­elated to differ­ences in cross-­sec­tional shape
Straight hair: round - Wavy: hair oval Curly hair: relatively flat
Color—due to pigment granules in the cells of the cortex
–Brown & black hair rich in eumelanin
– Red hair high concen­tration of pheome­lanin
– Blond hair has an interm­ediate amount of pheome­lanin and very little eumelanin
– Gray and white hair results from scarcity or absence of melanin in the cortex and the presence of air in the medulla
-Testosterone causes terminal hair in scalp to be replaced by vellus hair
-Hirsutism—excessive or undesi­rable hairiness in areas that are not usually hairy

Three types of skin cancer

• named for the epidermal cells in which they originate
-Basal cell carcinoma, squamous cell carcinoma, and malignant melanoma
-Person with metastatic melanoma lives only 6 months from diagnosis, 5% to 14% survive 5 years


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