Melanocytes – produce melanin; irregularly shaped
cells; s. basale
INTEGUMENTARY
SYSTEM
§
It consists of the skin, and accessory structures
such as hair, glands, and nails.
Functions of the Integumentary S. (PSVTE)
1. Protection
2. Sensation
3. Vitamin D production
4. Temperature regulation
5. Excretion
Cyanosis - bluish skin color; decreased blood O2
Carotene – yellow pigment in plants (squash, carrots);
source of vitamin A
Keratinization – cells change shape and chemical
composition; cells become filed with the protein keratin
(hard)
– transformation of the living cells
of the stratum basale into the dead squamous cells of the
stratum corneum
Stratum basale – deepest; cuboidal & columnar cells,
undergo mitosis every 19 days
Stratum corneum – most superficial stratum; dead
squamous cells filled with keratin (structural strength);
lipids (prevent fluid loss); joined by desmosomes
Callus – thickened area
Corn – bony prominence, thickened corn shaped
structure
Dermis
§ Dense collagenous connective tissue, contains
fibroblasts, adipocytes, macrophages
§ Nerves, hair follicles, smooth muscles, glands,
lymphatic vessels
Collagen (resist stretching) & elastic fibers – structural
strength
Cleavage lines/Tension lines – collagen fibers are
oriented in some directions; skin is most resistant to
stretch along these lines
Stretch marks – skin is overstretched, leaving lines that
are visible
Dermal papillae – contain blood vessels that supply the
epidermis with nutrients, remove waste products, and
regulate body temperature
Skin Color
Melanin – pigments responsible for skin, hair, eye color
yellow
(Caucasian),
Factors of Melanin Production
a. Genetic factors
b. Exposure to UV light
c. Hormones
Albinism - recessive genetic trait that causes deficiency
/ absence of melanin
Skin
Epidermis
§ Most superficial layer
§ Stratified squamous epithelium
§ In deepest layers, mitosis occurs
Melanin pigments –
(Asians), black (African)
Melanosomes – vesicles derived from GA where
melanin is produced
brown
Birthmarks – congenital disorder of the capillaries in the
dermis
Subcutaneous Tissue
§ Attaches the skin to underlying bones
§ Also called the hypodermis
§ Loose connective tissue
§ Storage of our body’s fat (padding, insulation)
Accessory Skin Structure
Hair
§ Columns of dead, keratinized epithelial cells
§ Produced in the hair bulb
Hair follicle – where each hair rises
Shaft – above the skin
Root – below the skin
Hair bulb – site of hair cell formation
Cortex – hard keratin
Medulla – soft central core
Cuticle – single layer of overlapping cells that holds the
hair in the hair follicle
Growth Stage
§ Hair is formed by epithelial cells within the hair
bulb
§ Divide and undergo keratinization
§ Hair root + shaft = columns of dead keratinized
epithelial cells
Resting Stage
§ Growth stops
§ Hair is held in the hair follicle
Next growth stage
§ A new hair is formed
§ The old hair falls out
Eyelashes – grow for about 30 days; rest for 105 days
Scalp hairs – grow for 3 years; rest for 1 – 2 years
Arrector Pili – smooth muscles; contraction = hair to
stand on end; produces goose bumps
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Glands
I.
Sebaceous Glands
§ Simple, branched acinar glands
§ Connected by a duct to the superficial part of
the hair follicle
§ Sebum – oily, white substance rich in lipids;
released by holocrine secretion; lubricates the
hair/surface of the skin (prevents drying and
protects against bacteria)
II.
3.
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Sweat Glands
a. Eccrine Sweat Glands
Ø Simple, coiled, tubular glands
Ø Release
sweat
by
melocrine
secretion
Ø Numerous in the palms and soles
b. Apocrine Sweat Glands
Ø Simple, coiled, tubular glands
Ø Produce a think secretion rich in
organic substances
Ø Released primary by melocrine
secretion; some glands demonstrate
holocrine secretion
Ø Open into hair follicles, in armpits
and genitalia
Ø Become active at puberty
III.
4.
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Other Glands
a. Ceruminous glands – cerumen (earwax)
b. Mammary glands – milk
Nails
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Dead stratum corneum cells
Contain a very hard type of keratin
Nail body – visible part of the nail
Nail root – part of the nail covered by skin
Cuticle – eponychium; s. corneum that extends onto the
nail body
Nail matrix – produces the nail
Nail bed – contributes to nail formation
Lunula – white, crescent-shaped area; part of the nail
matrix visible through the nail body
Physiology of the Integumentary S.
1. Protection
§ Reducing water loss
§ Prevents microorganisms from entering the
body
§ Protects underlying structures against abrasion
§ Hair on head = insulator
§ Eyebrows = keep sweat out of the eyes
§ Eyelashes = protects the eyes from foreign
objects
§ Hair in the nose, ears = prevents the entry of
dust
§ Nails = protect the ends of the fingers, toes from
damage; can be used in defense
2.
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5.
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Sensation
Sensory receptors for pain, touch, hot, cold,
pressure
Vitamin D Production
Skin
exposed
to
UV
light
produces
cholecalciferol (modified in the liver, then in the
kidneys to produce active vitamin D)
Best sources of Vit. D = fatty fish, vit. D
fortified milk
Small amounts of Vit D = eggs, butter, liver
Active Vit. D stimulates the small intestine to
absorb calcium and phosphate (normal bone
growth, normal muscle function)
Temperature Regulation
Normal body temp. = 37oC (98.6 oF)
Rate of chemical rxns within the body can
increased of decreased based on the body temp.
Factors that raise body temperature
Ø Exercise
Ø Fever
Ø Increase
in
environmental
temperature
The skin controls heat loss from the body
through dilation and constriction of blood
vessels
Sweat glands produce sweat, which evaporates
and lowers body temperature
Heat is lost by radiation (infrared energy),
convection (air movement), conduction (direct
contact)
Excretion
Skin glands remove water and salt
Also removes small amounts of urea, uric acid,
ammonia
Integumentary S. as a Diagnostic Aid
Cyanosis – bluish color to the skin caused by decreased
blod O2 content
Jaundice – yellowish skin color caused by liver damage
(viral hepatitis)
Rashes & lesions - symptoms of problems elsewhere;
e.g. Scarlet fever causes reddish rash, allergic reaction to
food or drugs can develop rashes
Vitamin A Deficiency – excess keratin; sandpaper
texture characteristic
Iron Deficiency Anemia – nails become flat or concave
Lead Poisoning – high levels of lead in the hair
Burns
Burn – injury to a tissue caused by heat, cold, friction,
chemicals, electricity, and radiation
I.
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Partial-thickness Burns
S. basale remains viable;
Regeneration of the epidermis occurs within the
burn area
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a.
First-degree burns
Ø Epidermis
Ø Red and painful
Ø Slight edema (swelling)
b. Second-degree burns
Ø Epidermis, dermis
Ø Epidermis regenerates from the
epithelial tissue
Ø Dermal damage is minimal;
v Redness, pain, edema, blisters
v Healing = 2 weeks
v No scarring
Ø Deep into the dermis
v Red, tan, or white
v Takes several months to heal
v Might scar
II.
Full-thickness Burns
a. Third-degree burns
Ø Epidermis, dermis, and underlying
tissues are completely destroyed
Ø Recovery occurs from the edges of
the burn wound
Ø Region of the 3rd degree burn is
painless (sensory receptors have
been destroyed)
Ø White, tan, brown, black, deep
cherry red
Ø Take a long time to heal
Ø Form scar tissue
Ø Skin grafts are used to prevent
complications and to speed healing
Skin Cancer
§ Most common type of cancer
§ Exposure to UV light from the sun
§ Usually on face, neck, hands
§ Most like to have skin cancer = fair skinned or
older than 50
§ Limiting exposure to sun, using sunscreen;
reduces the likelihood of developing skin cancer
§ Ultraviolet light
Ø UVA
v Longer wavelength
v Causes most tanning of the skin
v Development
of
malignant
melanoma
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III.
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Squamous cell carcinoma
Immediately superficial to the s. basale
Cells continue to divide as they produce keratin
= nodular, keratinized tumor confined to the
epidermis
Can invade the dermis, metastasize, and cause
death
Malignant melanoma
Rare form of skin cancer that arises from
melanocytes; usually from a pre-existing mole
Mole – an aggregation or nest of melanocytes
Large, flat, spreading lesion or deeply
pigmented nodule
Metastasis is common
Often fatal
FX of Aging on the Integumentary S.
§ Epidermis thins
§ Amount of collagen in the dermis decreases
§ Skin infections are most likely
§ Repair of skin occurs slower
§ Decrease no. of elastic fibers in the dermis and
loss of fat (sagging of skin, wrinkles)
§ Decrease of activity of sweat glands = reduced
ability to regulate body temp.
§ Decrease sebaceous gland activity = skin
becomes drier
§ Decrease no. of melanocytes
§ Some areas, the no. of melanocytes increase =
age spots
§ Increased melanin production = freckles; also,
gray/white hair
§ Skin that is exposed to sunlight = shows signs of
aging more rapidly
UVB
v Most burning of the skin
v Development of basal cell and
squamous cell carcinoma
Basal cell carcinoma
Most frequent type
S. basale and extends into the dermis to produce
an open ulcer
Cure; surgical removal or radiation therapy
Little danger of cancer to spread, metastasize
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