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what are skin appendeages?
- hair follicles - produce hair
- sebaceous glands - produce sebum
- eccrine sweat glands - sweat
- apocrine sweat glands - sweat +carbs, lipids, and proteins
layers of the hair
- outside -> inside:
- cuticle - squamous cells, on the outside (go from cuboidal and columnar to squamous, horizontal to vertical,
- cortex - around the medulla, heavily keratinized, compactly grouped, cuboidal cells
- medulla - in the middle, thick hairs, large, vaculoated, moderately keratinized cells
what is hair?
keratinized structure, dead like the stratum corneum is dead
where does most of the mitosis happen?
in the hair bulb
transition of cells?
cuboidal - squamous - vertical squamous (lay on each other like shingles on a house)
what do peripheral epithelial cells produce?
3 internal layers and external root sheeths - internal and external
when does keratinizaion begin?
shortly after cells leave the matrix
provide growht of hair, differentiate into keratin-producing cells of the hair and the internal root sheath
3 layers of internal root sheath:
- cuticle (diff from hair cuticle) - squamous cells whose outer free surface faces the hair shaft
- Huxley's layer - single of double layer of flattened cells that form the middle plate of the internal root sheath
- Henle's layer -outersingle layer of cuboidal cells in irect contact with the outermost part of hair follicle
differences between keratiniztion between epidermis and hair:
Epidermis produces a relatively soft keratinized outer layer of dead cells that adhere slightly to skin and desquamate continuously. In hair, has a hard and compact keratinized structure.
Keratinization in epidermis occurs continuously and over the entire surface. In hair it is intermittent and occurs only in hair root (required dermal papilla).
How does hair arise?
epidermal invagination - follicular bulge (off to the side) contains epidermal stem cells that provide growth of internal root sheath, cortex, medulla, and sebacious glands
where do melanocytes come from?
as basal cells of epidermis ingress they take melanocytes along with them
what type of secretion?
relation to hair
secrete sebum (an oily subtance that coats hair and skin surface)
holocrine (apoptosis - cell bursts)
normally there are a few located around each hair follicle
attaches at site of follicular bulge
opens into upper portion of hair follicle (except in glans penis, glans clitorus, and lips - opens directly onto surface of epidermis)
look at pic of hair follicle
What are the three variations in human hair production?
- Lanugo - embryonic
- vellus - short silky fine clear
- terminal - on armpits, head
how does vellus hair turn into terminal hair at puberty?
androgen hormone causes it and also stimulates new growth in armit and pubic area
what is the balding process?
conversion of follicles from vellus to terminal
how does hair differ around body parts?
cells know what they are supposed to e depending on WHERE they are
Stages of hair growth?
- anagen - more than 80% of follicles, active growth, mistosis in hair bulb
- catagen - transition phase where cells stop undergoing mitosis, only lasts a few weeks, bulb isnt nicely supporting hair anymore, formation of club hair
- telogen- 10-15%, resting phase, full club hair formed
why do eyebrows and eyelashes not grow as long?
shorter anagen phase
how long is scalp hair in anagen for?
when do sebaceous glands begin to fx?
how do sebaceous glands grow?
- Stem cells at base proliferate and differentiate, filling acini with rounded cells containing
- increasing amounts of fat droplets
Sweat Glands - classification?
eccrine - entire body surface except for lips and genitals, thermal regulation
apocrine - limited to mammary gland, skin around anus, external genitalia, underarms
misc. apocrine glands - ceruminous (earwax) glands and glands of Moll (eyelashes)
Eccrine sweat glands?
- simple coiled tubular glands
- regulates body T, cooling through evaporation (thermoregulatory sweating)
how is the sweat made in eccrine glands?
- big pic:
- Move things from the capillary to the lumen to make the sweat, shove everythign in there then the cells in the duct sort rhough it and take it back (kind of like the kidney)
- specifics: The sweat is produced in lower portion of the gland then works its way up to the surface, it is made very concentrated, body regulates how much of the stuff to take back and your body will reabsorb if you miss the mark
- ex: (chloride ions) people with cystic fibrosis they have no way to reabsorb the salt bc mutation in salt channel = salty skin
what is sweat made up of?
water, NaCl, urea, ammonia, uric acid
what are cells in sweat ducts responsible for? and what is their morphology?
- sodium absorption
- stratified cuboidal, no myoepithelium
what is fx of myoepithelial cells? where are they?
- they are contractile!
- the squeeze and push the sweat out to the surface
they are down in the bulb (secretory portion)
apocrine sweat glands?
fx? morphology? secretion?
coiled tubular, may be branched, open into hair follicles (areolar and anal regions)
much larger, proteinacious sweat that can harvest bacteria which makes it smell, also have pheremones
wide lumen, store the secretions there