1. hair, wool, feathers, scales Flashcards
Where do hairs, feathers and scales develop from?
Epidermis interacting with underlying mesenchymal tissue
How does hair develop?
- The ectodermal bud grows into the mesenchyme
- the bud differentiates + and there are indications of glands
- The hair follicle develops with other structures- sebaceous gland, sweat gland, arrector pill muscle
What is the structure of hair?
long, thin chain of keratin proteins composed of
- a central medulla
- a thick cortex
- an outer cuticle
What are the 3 types of hair?
-Wool
- Tactile
- guard
How do guard hairs lie and run?
lie against the skin and run in tracts of the same direction
give examples of species-specific guard hairs
Horses: mane/tail/fetlock
Pigs: stiff bristles
Cattle: long tail hairs
What is the structure of tactile hair?
-Reach deep into subcutis or even muscle
- dermal sheath surrounds the follicle that contains nerve endings
- surrounded by a venous sinus
What is the hair growth cycle?
- Anagen: growing phase, most follicles
- Catagan: transition phase, growth slows, atrophy of follicle
- Telogen: Resting phase, growth stopped, hair eventually breaks free and sheds
What are the 5 functions of hair?
- protection
- thermoregulation
- water resistance
- communication/ camouflage
- sensory
How are feathers homologous to hairs?
-keratin structures from the epidermis
- shared ancestory
what are the 2 epidermal layers in birds?
- stratum germinativum (basale)
- stratum corneum
what are the 3 bird glands?
- uropygial (preen)
- aural
- vent
what do developing feathers contain a core of?
vascular dermis
What is the structure of a feather?
- main shaft = RACHIS
- VANES either side
- made up of BARBS with interlocking BARBULES
- base of quill = CALAMUS
What are the 6 types of feather and what do they do?
- CONTOUR FEATHERS: includes flight feathers, streamlined, waterproof
- HYOPENNA: Associated with contour feathers
- DOWN FEATHERS: non-interlocking barbules trap air
- SEMI-PLUMES: fluffy insulators
- BRISTLES: sensory and protective
- FILOPLUMES: sensory and help with flight adjustment
what are the 6 flight feathers?
- primary
- primary covert
- secondary
- secondary covert
- marginal covert
- alula
What are powder down feathers?
- Feathers that produce a fine, waxy keratin powder
- similar function to preen gland which is for cleaning and waterproofing therefore most birds without a preen gland get these feathers
What are the 6 functions of feathers?
- protection
- water resistance
- thermoregulation
- communication/camouflage
- sensory
- flight/locomotion
What are the 3 layers of the epidermis in reptiles?
- Stratum germinativum
- stratum intermedium
- stratum corneum
reptiles + amphibians can sometimes have OSTEODERMS, what are these?
- Bony plates in the dermis
in tortoises what is the shell formed from?
osteoderm fusion with ribs
what do thick keratinised scales reduce? what is the risk from this?
skin sensation
risk of thermal burns
what is Ecdysis and what is it controlled by?
skin shedding
controlled by thyroid gland
what does ecdysis do and what is the risk from this to consider?
Replaces worn skin, making it more permeable and therefore more susceptible to infection/parasites/medication overdose
where are fish scales derived from?
are dermally derived from mesoderm
what cells do fish have little of?
keratinocytes and corneocytes
what is the lateral line system in fish and how is it achieved?
- It is a system of sensory organs in a fish achieved by modified epithelial cells
- it senses movement/vibration/ pressure in surrounding water that helps with orientation/defence/predation
