HAIR Flashcards
What is a hair follicle?
an extension of the epidermis
describe the simple hair follicle:
one, primary hair (known as guard hair)
describe the compound hair follicle:
one primary hair, plus multiple secondary (usually wool) hairs
what animals have simple hair follicles?
horses, cattle pigs humans
what animals have compound hair follicles?
dog, cat, sheep, goats
What are the three basic hair forms?
Guard hairs
Wool hairs
Tactile hairs
What are guard hairs?
stiff straight (topcoat)
What are wool hairs?
Fine wavy (undercoat)
What are tactile hairs?
sensory function (whiskers)
What can guard hair tracts help with?
promote water runoff
differences between guard hairs and wool hairs?
shorter, thinner, wavy
what is the advantage of wool hairs?
traps air between the wool fibres
blood sinus?
spaces around the hair follicle that contains blood - around tactile hair follicle
why blood sinus?
amplify vibrations - increase efficiency of sensory system
why do hairs shed?
they have come to the end of their lifecycle
when does shedding peak?
spring and autumn
what is shedding regulated by?
pineal gland
4 stages of hair lifecycle:
anagen, catagen, telogen, anagen (again)
Describe the anagen stage of the hair cycle:
growth phase - most follicles are in anagen
Describe the catagen stage of the hair cycle:
transition phase, growth slows, atrophy of follicle
Describe the telogen stage of the hair cycle:
resting phase, growth stopped, hair eventually breaks free and can be shed
Describe the anagen (again) stage of the hair cycle:
hair pushed out
5 functions of hair?
protection, water resistance, thermoregulation/insulation, commmunication/camouflage, sensory function
How can hair be useful for protection?
tough keratin hairs covering sensitive structures