Josh - hair Flashcards
(37 cards)
list hair function
thermal insulation, camouflage, disperstion of sweat and sebum and sensory/ tactile
what are the three layes of hair?
Cuticle: Outermost layer has scale like cells that overlap.
Cortex: strength, colour and texture of hair, has melanin
Medulla
where are melanocytes produced and by what
melanoblasts produce melanocytes which are kept in the medula.
describe key anatomy of the hair
Hair shaft: terminally differentiated dead keratinocytes, it projects from the epidermis.
Root: The part of the hair which is embedded in the skin
Hair follicle: Folding in of epidermal surface into dermis
Hair bulb: Expansion of follicle around root
Papilla: A bit of dermal tissue that protrudes into the hair bulb, contains capillaries to supply blood
Connective tissue root sheath: Wall of hair follicle, thickened basement membrane
what are the types of hair follicles
Primary: rooted in dermis with a large diameter, associated with sebaceous and sweat glands and arrector pili muscle
Secondary: narrower diameter, more superficial and may be associated with sebaceous gland but no sweat gland or muscle
Compound: One primary and several secondary follicles, fuse above sebaceous gland such that several hairs emerge from the surface
Sinus/ tactile: Vibrissae or whiskers with large single follicle, blood filled sinus in dermal sheath.
what are the three main types of hair in domestic species
Guard hairs: outer coat
Wool hairs: fine, often curly on other species often called undercoat.
Tactile hairs: long stiff hairs with specialised innervation that renders them effective as organs of touch
what are the three glands involed in hair
sebaceous, merocrine and apocrine
describe key features of the sebaceous gland
In the dermis they are attached to the hair follicles and are a branched acinar gland which produce sebum (lipid) via holocrine secretion.
Single layer of cuboidal cells peripherally on basement membrane
Towards centre, cells become polyhedral and accumulate lipid, nuclei become pyknotic
Secrete into hair follicle through short duct lined by stratified squamous epithelium
describe key features of the merocrine gland
Located in foot pads and furless areas they secrete thin sweat from simple tubular glands. Secretion:
Lined by cuboidal dark and clear cells
Clear cells have lipid inclusions and produce aqueous sweat
Lined by stratified cuboidal epithelium
Open onto epidermal surface
describe key features of the merocrine gland
In most areas it produces a viscous sweat that is often used for pheromones from simple tubular glands.
Lined by simple cuboidal to columnar epithelium
Myoepithelial (muscle squeezing) cells between secretory cells and basal lamina
Opens into the hair follicle just below the skin.
descrbe the diffrence of secretion in apocrine, merocrine and sebaceous glands
merocrine: small vesicles release liquid via exocytosis
apocrine: portions of the cuboidal cells cytoplasm are pinched of and released
sebaceous: holocrine release through cell divison and release.
Broadly explain the three phases in hair lifecycle
Anagen: Active growth phase until fully mature
Catagen: Regression of hair follicles, lower cycling portion is degraded
Telogen: Resting phase
is hair growth continous?
no
why is woll diffrent from regular
has NO medulla, the fleece is soft and the curls are crimps, it lacks guard has, in marino they have little guard hairs (secondary hairs) but in tukidale they have a mix of both, hence they produce rougher material like carpet.
is a woll has many secondary hairs with only 1-2 primary, what species is it likey to be?
merino
Explain the stages during the initiation of a hair/wool follicle
Proliferation of epidermal cells to form a placode
Beneath the placode there is dermal condensate being formed
These two cell formations grow down together into the dermis
Progressively, the dermal cells move into the epithelial bud to form the pre-papilla
Finally epithelial bulb cells envelop the pre-papilla as the follicle lengthens and descends into the dermis
what type of hair follicles are developed first
The first follicles the are formed – primary follicles
Then secondary follicles develop
Followed by secondary-derived follicles that branch out from the secondary follicles
what makes primary follicles diffrent from secondary?
more likley to have sebaceous/ sweat gland.
has arrector pili muscle
larger diameter
what is a suit gland?
sweat gland in a merino
Describe how amino acids regulate hair growth
Amino acids: all are required to make keratin
are cystenine and methionine important?
yes
Describe how folic acid regulate hair growth
improves methionine synthesis which controls hair growth
Describe how vitamin B regulate hair growth
(biotin, riboflavin) are important
Describe how vitamin D regulate hair growth
stimulates hair follicle keratinocyte differentiation and induces numerous hair keratin genes
