Integumentary system

1. M o r a n o , M . A .
I N T E G U M E N T A R Y
S Y S T E M
§ 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
Skin
Epidermis
§ Most superficial layer
§ Stratified squamous epithelium
§ In deepest layers, mitosis occurs
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
Melanin pigments – yellow (Caucasian), brown
(Asians), black (African)
Melanocytes – produce melanin; irregularly shaped
cells; s. basale
Melanosomes – vesicles derived from GA where
melanin is produced
Factors of Melanin Production
a. Genetic factors
b. Exposure to UV light
c. Hormones
Albinism - recessive genetic trait that causes deficiency
/ absence of melanin
Cyanosis - bluish skin color; decreased blood O2
Carotene – yellow pigment in plants (squash, carrots);
source of vitamin A
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

2. M o r a n o , M . A .
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. 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. Other Glands
a. Ceruminous glands – cerumen (earwax)
b. Mammary glands – milk
Nails
§ 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. Sensation
§ Sensory receptors for pain, touch, hot, cold,
pressure
3. 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)
4. Temperature Regulation
§ Normal body temp. = 37o
C (98.6 o
F)
§ 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)
5. 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. Partial-thickness Burns
§ S. basale remains viable;
§ Regeneration of the epidermis occurs within the
burn area

3. M o r a n o , M . A .
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
Ø UVB
v Most burning of the skin
v Development of basal cell and
squamous cell carcinoma
I. 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
II. 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
III. 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