Studied by 8 people
what are 4 ways the skin impacts body temperature?
sweat & vasodilation (cool down), adipose & hair (insulate)
how does the skin protect the body?
mechanical injury, infection, UV, dehydration
what does the skin excrete?
heat, water, salt
how much blood does the skin hold? explain why we get pale
8-10% of total blood volume. we get pale when cut because body constricts bv’s & pull blood from skin
what are 6 skin functions?
body temp
protection
sensation
excretion
blood reservoir
immunity
the skin is a large organ composed of all ___ tissue types
4
the superficial epidermis consists of which tissue?
epithelial tissue
the deeper dermis consists of which tissue?
connective tissue
which layer is not technically a part of the skin?
deep subcutaneous layer/hypodermis
the deep subcutaneous layer is made of what 2 tissues?
areolar & adipose
what is thermoregulation?
what type of feedback is it?
what are the affectors, control center, & effectors?
body temp homeostasis. negative. skin thermoreceptors (sense temp). hypothalamus. sweat glands & bv’s
name the 5 layers of the epidermis in order from top to bottom
stratum corneum
stratum lucidum
stratum granulosum
stratum spinosum
stratum basale
the epidermis contains stratified squamous epithelium. it is avascular. it has 4 types of cells & HOW MANY distinct strat (layers) of cells?
4-5
describe keratinocytes
produce the protein keratin. protect skin from heat, microbes, chemicals, lamellar granules (release waterproof sealant)
describe melanocytes
produce melanin → skin color & absorb damaging UV
describe langerhans cells
derived from bone marrow. immune response
describe merkel cells
sensation of touch
_____ keratinocytes are found on the very top layer of skin. they are inactive & mostly keratin.
dead
the very top layer of skin is called the _____ surface
apical
cells transform as they move up through the skin layers over what period of time?
1 month
describe the stratum corneum
many layers. dead cells shed continuously. lipids make it water repellant
describe the stratum lucidum
dead cells. high wear areas only (finger tips, palms, soles)
describe the stratum granulosum
flat dying cells. secrete lipids → waterproof
describe the stratum spinosum
most melanin here
describe the stratum basale
new cells - mitosis. basement layer
define calluses
constant exposure to friction causing corneum layer to abnormally thicken
describe psoriasis
chronic skin disorder. rapid division/movement of keratinocytes. cells shed in 7-10 days as flaky silvery scales
why would there be a need for a skin graft?
injury penetrates through epidermis & gets to stratum basale → skin can’t heal from the bottom up → takes long time to heal
what’s an autograft?
cover would with healthy skin from self
what’s an isograft?
skin graft from twin
what is autologous skin?
transplantation of patient’s skin after growing in culture
where is the dermis located?
below epidermis
what is the dermis?
what is it composed of?
what does it contain?
connective tissue layer made of collagen fibers, elastic fibers, fibroblasts, macrophages, & fat cells. contains hair follicles, glands, nerves, & bv’s
what are the 2 major regions of the dermis? (where are each located relative to each other?)
papillary region (superficial) & reticular region (deep)
what part of the dermis produces fingerprints?
dramatic lifts → epidermal ridges
what are stretch marks called? how do they occur? what are they made of?
striae. dermal tears from extreme stretching. dermis not growing fast enough. collagen heals the dermal tears, so they’re scars.
describe dermatoglyphs
fingerprints left by sweat glands open on ridges. increase grip
why don’t twins have identical fingerprints?
chance differences in tissues during development due to environment
what are the 2 types of sweat? which has to do with fingerprints?
liquid sweat & oil sweat. oil
what are lines of cleavage?
how do they impact surgeons & patients?
indicate the predominant direction of the underlying collagen fibers. incisions made parallel to them make a much smaller scar than those made perpendicular to the lines
what is thin skin & where is it found?
covers all parts of body except palms, digits, soles. lacks epidermal ridges. has less sensory receptors.
what is thick skin & where is it found?
covers palms, digits, soles. has thick epidermal ridges. lacks hair follicles & arrector pili muscles. has more sebaceous glands & sweat glands than thin skin
what are tattoos
injection of permanent dye into dermis
what colors does melanin range from?
yellow to black
melanin is an ____ pigment
epidermal
what are ethnic differences of melanin
same number of melanocytes. variances in amount of melanin production (how active they are)
melanin requires tyrosine. what happens when there is a lack of tyrosine?
albinism or vitiligo
what 4 areas is melanin most common?
extremities, genitals, nipples, face (extremeties & face likely because ancestors needed extra protection from being in the sun alot)
clusters of melanin cause what 2 things?
freckles & age spots
what are freckles called? define them.
ephilides. localized accumulation of melanin in keratinocytes at sun exposed areas. common in fair skinned/red headed people)
what are age spots called? define them.
solar lentigines. localised proliferation of melanocytes. middle age/sun damage. larger & more defined than freckles. don’t disappear in the winter
what is the name for chicken skin? what causes it?
keratosis pilaris. harmless skin condition. buildup of keratin blocks follicles. small, hard bumps. disappear with age
explain skin color inheritance
polygenic inheritance (many genes affect skin color). more activated genes = darker skin)
what color do carotene pigments cause?
where are they located?
which vitamin is a precursor?
what causes excessively this color of skin?
yellow → orange. dermis. vitamin A. carrots are absorbed but don’t break down, so orange pigment goes to skin, causing orange skin
what colors do hemoglobin pigments cause?
what is the reason for each color?
where is it found?
red (oxygenated), pink (deeper, oxygenated), purple (deoxygenated). [amount of O2]. dermis
what is jaundice?
yellowish color of skin & whites of eyes. buildup of yellow bilirubin in blood from liver disease
what is cyanosis
bluish color to nail beds & skin. hemoglobin depleted of oxygen looks purple-blue
what is erythema?
redness of skin due to enlargement of capillaries during inflammation, infection, allergy, or burns
what are 6 epidermal derivatives
hair
sudoriferous glands (sweat)
sebaceous glands (oil)
ceruminous glands (wax)
nails
dermatoglyphs
describe hair shaft
project above skin. dead keratinized cells
what do round & oval hair shafts indicate?
round = straight. oval = curly
where is the hair root located?
below skin
where is the hair medulla?
innermost layer
where is the hair cortex?
middle layer, pigment
where is the hair cuticle layer?
outer layer, keratinized cells
where is the hair follicle?
surrounds root
what are the 2 types of sheaths are involves with hair follicles?
external root sheath & internal root sheath
where is the hair bulb located?
base of follicle
what is hair papilla?
areolar connective tissue; matrix (germinal layer = hair growth)
what are arrector pili?
what is their purpose?
smooth muscle; elevates hair for insulation & minimizes air flow
what is the purpose of hair root plexus?
touch
what are the 6 layers of the hair root & follicle
medulla, cortex, cuticle, internal root sheath, external root sheath, dermal root sheath
what is terminal hair of the scalp?
longer & thicker than vellus hair. always associated with sebaceous gland to keep hairs flexible
what are the 2 basic kinds of hair? give examples of each
vellus: arms, legs
terminal: scalp, eyelashes, eyebrows, androgen-sensitive areas
what factors impact the growth of scalp hair?
illness, diet, surgery, hormones, chemo
at what length does hair usually stop growing? why?
2-3 feet. theory is that force of gravity is detected by matrix cells
what are the 3 functions of scalp hair?
cushion, from injury, uv protection, insulation
what 2 things cause male pattern baldness?
DHT (type of testosterone) & genetics
what is lanugo
fine, nonpigmented hair covering fetus
what is vellus
short, fine hair replacing lanugo. sense of touch
what is gooseflesh
raises hair to prevent heat loss
what does nasal hair do
filters & protects airways/lungs
what is the purpose of axillary hair & pubic hair?
possibly to enhance pheromone release
- (pheromones: chemicals released from 1 individual that effects other individual)
not well understood
associated with oily sweat glands
sex hormones here
hairs release pheromones
define hirsutism
increased number of hairs in androgen sensitive areas on females
hirsutism occurs because of high androgen levels. where do these high levels come from?
adrenal glands
what is hypertrichosis
increased hair growth in non-androgen sensitive areas
what are 2 types of hair removal? what is the difference between them?
electrolysis: permanent
laser therapy: temporary
mechanical hair removal [does/doesn’t?] cause hair to grow more rapidly, but sometimes thicker diameter
doesn’t
what are the 4 types of skin glands?
sebaceous (oil)
sudiferous (sweat)
ceruminous (wax)
mammary (milk)
which type of gland connects to hair follicles to keep hair shafts flexible?
sebaceous
where are sebaceous glands NOT located?
palms & soles
what is sebum
skin oil
sebum
contains cholesterol, proteins, fats, salts
moistens hair
_____ & softens skin
inhibits growth of what 2 things?
waterproofs
bacteria & fungi
where do blackheads get their color from?
melanin
acne
cystic can lead to scarring
bacterial inflammation of _____
secretions are stimulated by _____ at puberty
glands
androgens
how does acne occur?
bacteria → inflammation → duct closes → infection can’t get released → builds up
what are 2 types of sudoriferous glands?
eccrine & apocrine
what other type of gland is histologically similar to sudoriferous glands?
mammary
where are eccrine glands located?
most areas of skin - hands, feet, forehead
does this refer to eccrine or apocrine sweat glands?
ducts terminate at pores at the surface of the epidermis
eccrine
