Accessory Structure of the Skin Flashcards
structure of hair
columns of dead, keratinized cells that are fused together. shaft, root, bulb, papilla
function of hair.
covers all surfaces of the body except palms, soles, eyelids, lips, and nipples.
function of scalp hair.
reduces heat loss and provides protection from ultraviolet radiation
function of eyebrows
enhance facial expression and non-verbal communications.
function of eyelashes
shield eyes from rain and windblown debris
function of guard hairs
prevents foreign particles from entering the nostrils or ear canals.
shaft.
portion of a hair above the skin surface.
root
deep to the shaft and is surrounded by the tube called the follicle.
bulb
swelling at the base of the follicle from which hair originates.
papilla
contains blood vessels to nourish hair.
layers in the hair.
inner medulla, cortex, cuticle.
inner medulla.
contains air spaces. (not solid)
cortex
densely packed keratinized cells
cuticle
single layer of overlapping scaly cells as cuticles wear away, keratin fibrils spill out of cortex and medulla causing ‘split-ends’ to develop.
hair texture.
related to cross-sectional shape of the hairs.
hair color
due to the type and amount of pigment in each hair.
hair shafts are flat and ribbon-like
kinky hair texture.
hair shafts are oval
silky and wavy hair texture.
hair shafts are round
straight/ coarse hair texture.
hair growth cycle.
- stem cells from the follicle multiply and push the papilla deeper into the skin
- cell in the root sheath transform into hair cells that synthesize keratin.
- hair goes into a resting phase and eventually fall out.
how much does scalp hair grow.
1mm every three days. 10-18 cm every year (7in).
alopecia
hair growth slow down around the age of 40 (hair loss) because of aging, disease, or poor nutrition or medical treatment.
pattern baldness
genetic condition expressed in individuals with high testosterone.
arrector pili muscle
smooth muscle and is associated with each hair.
“goose bumps”
cold temp., fright, or emotional stress can cause these muscles to contract and pull a hair into a vertical position.
description
plates of hard, keratinized cells that form protective coverings over the dorsal surface of the terminal portion of the fingers and toes.
free edge.
portion of the nail that extends beyond the end of the digit.
lunule
small white area at the proximal end of the nail body
cuticle
dead epidermis that covers the proximal end of the nail (protection of nail matrix).
what causes nail to grow.
mitosis from the nail matrix at a rate of 1 mm per week.
structure of sebaceous (oil) glands.
usually connected to hair follicles, although some of them open directly to the surface of the skin.
function of sebum
keep hair from dying out and turning brittle, keep skin soft and moist to inhibit growth of certain bacteria. secreted from oil glands.
what happens when there is accumulation of sebum
in facial sebaceous glands causes blackheads which can lead to the formation of pimples if they become infected with bacteria.
what does the Sudoriferous (sweat) gland do?
produces a mixture of water, salts, and organic compounds.
function of sweat?
regulates body temperature by providing a cooling mechanism and also eliminates urea, lactic acid, ammonia, and some drugs from the body “precipitation.”
Two types of sweat gland.
eccrine and apocrine.
Define eccrine.
3 to 4 million distributed through-out the skin, palms, soles, forehead, produce watery perspiration.
Define apocrine
located in the armpits, pubic area, breast and beard area of mature males where their ducts lead to nearby hair follicles rather than to the surface of the skin.
How do apocrine differ from eccrine?
apocrine produce viscous perspiration.
Apocrine does not develop till puberty and response to emotional stress and sexual arousal
females have enlarge glands that shrink during menstrual cycle.
