Structure and function of hair Flashcards
Where does all hair develop from?
Hair develops from the epidermis
What is the basic structure of hair?
long thin chains of keratin, composed of a central medulla, thick cortex and outer cuticle
What are the three basic hair forms?
Stiff guard hairs, Wavy wool hairs and long tactile hairs
How does hair develop?
Ectodermal bud grows into a mesenchyme, the bud differentiates and a developed hair follicle forms
What are Guard and Wool hairs like in dogs and cats?
several hairs with a single follicle opening, one guard hair with several secondary wool hairs
What are some examples of guard hairs?
Manes in horses, spines of hedgehogs, beards of goats
What are the 3 growth stages for hair?
Anagen, Catagen, Telogen
What occurs in anagen?
It is the growing phase, new keratin is pushed upwards
What occurs during Catagen?
It is the transition phase, growth slows and the follicle shrinks
What occurs during Telogen?
Telogen is the resting phase, Growths stops and the hair breaks free and is shed
What are 7 functions of hair?
Cover sensitive structures, direct water, insulation, protection, camouflage
How many epidermal layers do birds have?
2, stratum germinativum and stratum corneum
What are the 3 glands birds have?
Uropygial gland, Aural gland and the Vent gland
What are the 4 parts that make up the main structure of a feather?
Main shaft (rachis), Vanes either side, barbs with interlocking barbules and the base of the quill (calamus)
What are contour feathers?
form the main surface of a bird, streamline and waterproof- can be primary or secondary
What are down feathers?
they have a loose structure that interlocks and traps air for an insulation function
What are bristle feathers?
Simple feathers, lack barb branches and have a sensory and protective function
What are filoplumes?
hairlike feathers with a few soft barbs, can have a sensory function
What is the function of the preen gland?
to waterproof the feathers by distributing preen oil
What is the function of powder down feathers?
more prevalent in birds without a preen gland, produce fine waxy keratin powder
How many layers does the reptile epidermis have?
3, germinativum, intermedium and corneum
What are osteoderms?
bony plates in the dermis
What are some special considerations in reptiles?
Thick keratinised scales reduce skin sensation, and they have cutaneous appendages with different functions
What is Ecdysis?
Skin shedding, controlled by the thyroid gland- makes skin more permeable and susceptible to underlying disease
What is Dysedysis?
an abnormal pattern of shedding
Where are fish scales dermally derived from?
The mesoderm
Extra notes on fish?
They have little keratinisation/ corneocytes so their skin is more permeable than other species
What is the name of guard hairs in sheep?
Kemp Hairs
Where are sebaceous glands found and why?
Attached to the hair follicle, because they produce an oily secretion that enters the hair
Where do hair feathers and scales develop from?
Epidermis interacting with underlying mesenchymal tissue
What controls Ecydysis?
The thyroid gland
What type of feathers contain a core of vascular dermis?
Developing feathers
What gland regulates shedding?
Pineal gland
