HAIR Flashcards

1
Q

What is a hair follicle?

A

an extension of the epidermis

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2
Q

describe the simple hair follicle:

A

one, primary hair (known as guard hair)

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3
Q

describe the compound hair follicle:

A

one primary hair, plus multiple secondary (usually wool) hairs

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4
Q

what animals have simple hair follicles?

A

horses, cattle pigs humans

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5
Q

what animals have compound hair follicles?

A

dog, cat, sheep, goats

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6
Q

What are the three basic hair forms?

A

Guard hairs
Wool hairs
Tactile hairs

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7
Q

What are guard hairs?

A

stiff straight (topcoat)

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8
Q

What are wool hairs?

A

Fine wavy (undercoat)

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9
Q

What are tactile hairs?

A

sensory function (whiskers)

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10
Q

What can guard hair tracts help with?

A

promote water runoff

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11
Q

differences between guard hairs and wool hairs?

A

shorter, thinner, wavy

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12
Q

what is the advantage of wool hairs?

A

traps air between the wool fibres

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13
Q

blood sinus?

A

spaces around the hair follicle that contains blood - around tactile hair follicle

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14
Q

why blood sinus?

A

amplify vibrations - increase efficiency of sensory system

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15
Q

why do hairs shed?

A

they have come to the end of their lifecycle

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16
Q

when does shedding peak?

A

spring and autumn

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16
Q

what is shedding regulated by?

A

pineal gland

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17
Q

4 stages of hair lifecycle:

A

anagen, catagen, telogen, anagen (again)

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18
Q

Describe the anagen stage of the hair cycle:

A

growth phase - most follicles are in anagen

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19
Q

Describe the catagen stage of the hair cycle:

A

transition phase, growth slows, atrophy of follicle

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20
Q

Describe the telogen stage of the hair cycle:

A

resting phase, growth stopped, hair eventually breaks free and can be shed

21
Q

Describe the anagen (again) stage of the hair cycle:

A

hair pushed out

22
Q

5 functions of hair?

A

protection, water resistance, thermoregulation/insulation, commmunication/camouflage, sensory function

23
Q

How can hair be useful for protection?

A

tough keratin hairs covering sensitive structures

24
Q

how can hairs help with thermoregulation?

A

wool hairs trap air, arrector pili + guard hairs, some sweat glands open into the follicle

25
Q

how can hairs help with communication/camouflage?

A

colours, arrector pili, glands opening into follicle

26
Q

How many epidermal layers do birds have?

A

2

27
Q

what are the two epidermal layers of the birds?

A

stratum germinativum (basale)
stratum corneum

28
Q

how many glands do birds have?

A

only 3 - essentially glandless

29
Q

name the three glands a bird has:

A

uropygial (preen) gland
aural gland
vent gland

30
Q

what do developing feathers contain?

A

a core of vascular dermis (a blood feather) - therefore it may bleed if plucked or broken

31
Q

difference between contour and down feathers:

A

contour feathers have interlocking barbules whereas down feathers don’t but this makes them good at trapping air

32
Q

how many types of feathers are there?

A

6

33
Q

what is the rachis?

A

main shaft of the feather

34
Q

what is the calamus?

A

the base of the quill

35
Q

tactile hairs equivalent in birds are called?

A

bristle hairs - on faces of some birds

36
Q

if birds don’t have a preen gland, what do they have in more abundance?

A

powder down feathers

37
Q

describe the powder found in powder down feathers?

A

fine, waxy keratin powder

38
Q

what causes allergy to birds?

A

the powder found in powder down feathers

39
Q

how many layers does the reptile epidermis have? name them

A

3
stratum germinativum (=basale)
stratum intermedium
stratum corneum

40
Q

what are scales homologous to?

A

to hairs and feathers

41
Q

hairs, feathers, scales are all homologous meaning?

A

shared ancestry - all keratin structures from epidermis

42
Q

Why can reptiles risk thermal burns?

A

thick keratinised scales which reduce skin sensation

43
Q

what is ecdysis?

A

skin shedding

44
Q

what is skin shedding controlled by?

A

the thyroid gland

45
Q

what is dysecdysis?

A
46
Q

in reptiles skin is more permeable (when shedding), meaning?

A

more susceptible to parasites, infection and medication overdose

47
Q

what happens to snakes when they are shedding?

A

they go blind - so have a behavioural change

48
Q

why do snakes go blind during shedding?

A

the clear spectacle scale over the eye goes opaque as it separates

49
Q

what is the additional organ that fish have which other organisms do not?

A

lateral line system

50
Q
A