surface area of the skin
1.8 m^2
covers the entire surface of the body
skin
skin is comprised of what types of tissue
ALL 4 types:
- epithelial
- muscular
- nervous
- connective
other names for the integumentary system
- cutaneous membrane
or
- the integrument
name the 2 regions of the skin:
1. epidermis
2. dermis
attaches the skin to underlying tissue
hypodermis (or subcutaneous tissue)
- outer, thinner region
- lacks blood vessels & has tightly packed cells
- made of stratified squamous epithelium
- 5 layers (strata) ~ deep to superficial
epidermis
what are the 5 layers (strata) of the epidermis?
1. stratum basale
2. stratum spinosum
3. stratum granulosm
4. stratum lucidum
5. stratum corneum
- just superficial to dermis
- constantly dividing; new cells are pushed to the surface, then die & are sloughed off
stratum basale
Cells:
most numerous; produce keratin
keratinocytes
a waterproofing protein
keratin
Cells:
macrophages, a type of white blood cell that phagocytize microbes & then travel to lymphatic system to stimulate the immune system
langerhans cells
Cells:
produce melanin; skin color & protection from UV radiation
melanocytes
Sensory Nerves:
pain & temperature sensations
free nerve endings
Sensory Nerves:
touch sensations
tactile cells (Merkel cells)
- cells can still divide by mitosis
- spiny appearance due to keratin fibers
stratum spinosum
- flattened cells
- contain a lot of keratin & dark-staining pigment granules
- cells are tightly sealed together to form an effective barrier
stratum granulosum
- just deep to stratum corneum
- found only in thick skin (palms of the hand, soles of feet, & elbows)
- provides protection from constant friction
stratum lucidum
- tough, uppermost layer of epidermis
- cells are keratinized (hardened) and dead
- keratin prevents water loss & water gain
- serves as a mechanical barrier against microbes
stratum corneum
- thicker than epidermis
- dense, irregular connective tissue
- numerous sensory nerve fibers
dermis
- fingerlike projections that project into & anchor the epidermis
- they cause ridges in the overlying epidermis which result in fingerprints
dermal papillae
_________ fibers prevent skin from being torn (location: dermis)
collagenous
__________ fibers stretch to allow movement of muscles & joints (location: dermis)
elastic
____________ of dermis supplies oxygen & nutrients to cells of dermis causes temporary changes to skin color (location: dermis)
vascularization
- subcutaneous layers located below the dermis
- composed of loose connective tissue
hypodermis
_________ tissue provides energy storage, insulation, & protective padding (location: hypodermis)
adipose
characterized by excessive body & facial hair in women due to increased production of male sex hormone, treated with injections to kill the hair roots
hirsutism
hair loss
alopecia
male pattern baldness, inherited
androgenic alopecia
sudden onset of patchy hair loss
alopecia areata
- formed from epidermal cells
- located in dermis
hair follicles
portion of hair within follicle
hair root
portion of hair that continues beyond the skin
hair shaft
smooth muscle attached to hair follicle, when contracted it causes the hair to stand up, this causes "goose bumps
arrector pili muscle
formed from specialized epithelial cells
nails
base of the nail
nail root
visible portion of the nail
nail body
fold of skin that hides the root
cuticle
area of rapidly dividing cells, whitish color
lunula (moon)
groups of specialized cells that produce & secrete substances into ducts
glands
Glands:
- present in all regions of the skin; some become more active under stress
- can be as many as 90 glands per square centimeter on the leg & 400 glands per square centimeter on the palms & soles
sweat (sudoriferous) glands
Glands:
- open into hair follicles in anal regions, groin, & armpits
-begin to secrete at puberty
- mammary glands are modified apocrine glands that produce milk only after childbirth
apocrine glands
Glands:
- open onto surface of skin
- active when body heats up; helps lower body temperature
- sweat (perspiration) is mostly water, but also excretes wastes
eccrine sweat glands
Glands:
- modified sweat glands that produce cerumen (earwax)
ceruminous glands
Glands:
- most are associated with a hair follicle
- secrete an oily substance called sebum
sebaceous galnds
inflammation of the sebaceous glands
acne vulgaris
fungal infection often involving skin of the toes & soles
athlete's foot
bacterial infection common in young children, results in pustules that crust over
impetigo
yeast infection mainly in moist areas
candidiasis
inflammation of the skin bc of sensitivity to various chemicals (soaps, detergents)
eczema
caused by a dry scalp producing flaking & itching
dandruff
allergic reaction causing reddish, elevated, & often itchy patches
urticaria (hives)
- classified as either melanoma or nonmelanoma
- begins with mutation of the skin cell DNA
skin cancer
(melanoma/nonmelanoma) cancers - less likely to metastasize
nonmelanoma
2 types of nonmelanoma cancers
1) basal cell carcinoma
2) squamous cell carcinoma
- most common type of skin cancer
- UV radiation causes epidermal basal cells to form a tumor, while suppressing the immune system's ability to detect the tumor
basal cell carcinoma
- 5x less common than basal cell carcinoma
- begins the superficial cells of the epidermis
- more likely to spread than basal cell carcinoma
- about 1% of cases result in death
- triggered by excessive UV exposure
squamous cell carcinoma
(melanoma/nonmelanoma) - most likely to be malignant
melanoma
- starts in the melanocytes
- has the appearance of an unusual mole, or a spilled ink spot
- most common in fair-skinned people
- mole may be elevated above the skin surface, and the skin around it turns gray, white, or red
- increases with the number of
melanoma
5 ways to avoid skin cancer:
1) use broad-spectrum sunscreens of at least SPF15
2) wear protective clothing to cover skin
3) wear a wide brimmed hat
4) wear UV sunglasses
5) stay out of the sun between 10 am & 3 pm
* avoid tanning machines
4 ways wrinkles form:
1) loose epidermis
2) fewer fibers
3) less padding in hypodermis
4)UV damage
6 functions of the skin:
1) help prevent bacterial invasion
2) regulation of water loss & gain
3) assists the urinary system
4) vitamin D production
5) gathers sensory information
6) helps regulate body temperature
(sensible/insensible)
can be felt as water evaporates from the body
sensible
(sensible/insensible)
occurs without one's awareness as water evaporates from the bldy
insensible
body temperature above normal
hyperthermia
examples of hyperthermia:
- heat exhaustion: high body temperature, low blood pressure, profuse sweating, loss of salts
- heat stroke: elevated temperatures, no sweating
body temperature below normal
hypothermia
examples of hypothermia:
- uncontrollable shivering, incoherent speech, lack of coordination
leads to slow pulse, unconsciousness, shallow breathing, & death