2.5: accessory structures: hair, nails, glands

composition of hair

row of keratinized squamous epithelial cells

-hair is found everywhere on the body except areas of thick skin

structure of hair

-shaft: exposed to external environment, contains dead cells

-root: internal

root of hair: hair follicle

layer of epidermal tissue anchoring root into dermis

root of hair: matrix

actively dividing stem cells above hair papilla (for blood supply)

root of hair: arrector pili

connected to hair follicle; smooth muscle, contract to cause piloerection

hair shaft composition

-medulla: core of loosely arranged cells made from soft keratin

-cortex: several layers of complex hard keratinocytes, site of pigmentation

-cuticle: single layer of overlapping cells, most highly keratinized region

split ends

damage to cuticle exposes underlying ayers

types of hair: lanugo

unpigmented hair in developing fetus, insulative purpose

types of hair: vellus

fin, thin body hair

types of hair: terminal

thicker hairr making up eyebrows, lashes, scalp

-after puberty, terminal hair grows in pubic region

-in males, facial, trunk, limbs

texture of hair is dictated by

shape of follicle

color of hair is dictated by

melanin pigment in hair shaft: eumelanin or pheomelanin

hair growth cycle: anagen

active cell division, utilize nourishing blood supply, get pushed superficially

hair growth cycle: catagen (transition phase)

stop cell division, detaches from nourishing blood supply

hair growth cycle: telagen (resting phase)

without nourishment, hair dies & falls outt

scalp hair: in anagen for __ years, high/ how mitotic rate

~6 years, higher mitotic rate

lashes & brows: in anagen for __ days, high/ how mitotic rate

~30 days, low mitotic rate

composition of nails

-hard keratin, no melanocytes

-external: nail plate

-nail bed: underlying nail plate

-nail matrix: site of nail growth

functions of nails

protection, object manipulation

glands

groups of modified epithelial cells located in dermis

exocrine glands & types of glands

release non-hormonal secretions secretions

-sweat

-sebaceous

*eccrine sweat glands

-abundant throughout body

-sweat secreted into skin surface via ducts

-99% water, solutes & bactericidal liquid

-thermoregulation

-emotional sweating begins on palms & spreads elsewhere

apocrine sweat glands

-only in genital regions

-nonfunctional until puberty

-sweat released through hair follicles

-bacterial activities on surface with sweat produce odor

ceruminous glands: modified sweat

-found in lining of ear canal

-secrete cerumen for lubrication & protection

mammary glands

-found in adipose tissue of breasts

-secrete milk: proteins, lipids, carbs

-present in males & females

-develop only during pregnancy & lactation

sebaceous glands (structurally different from other glands)

-most numerous on face & scalp

-secrete into hair follicle

-largely inactive until puberty

-secrete sebum: lubricates/ waterproofs skin & hair, bactericidal properties