HAIR

Question 1

What is a hair follicle?

Answer 1

an extension of the epidermis

Question 2

describe the simple hair follicle:

Answer 2

one, primary hair (known as guard hair)

Question 3

describe the compound hair follicle:

Answer 3

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

Question 4

what animals have simple hair follicles?

Answer 4

horses, cattle pigs humans

Question 5

what animals have compound hair follicles?

Answer 5

dog, cat, sheep, goats

Question 6

What are the three basic hair forms?

Answer 6

Guard hairs
Wool hairs
Tactile hairs

Question 7

What are guard hairs?

Answer 7

stiff straight (topcoat)

Question 8

What are wool hairs?

Answer 8

Fine wavy (undercoat)

Question 9

What are tactile hairs?

Answer 9

sensory function (whiskers)

Question 10

What can guard hair tracts help with?

Answer 10

promote water runoff

Question 11

differences between guard hairs and wool hairs?

Answer 11

shorter, thinner, wavy

Question 12

what is the advantage of wool hairs?

Answer 12

traps air between the wool fibres

Question 13

blood sinus?

Answer 13

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

Question 14

why blood sinus?

Answer 14

amplify vibrations - increase efficiency of sensory system

Question 15

why do hairs shed?

Answer 15

they have come to the end of their lifecycle

Question 16

when does shedding peak?

Answer 16

spring and autumn

Question 16

what is shedding regulated by?

Answer 16

pineal gland

Question 17

4 stages of hair lifecycle:

Answer 17

anagen, catagen, telogen, anagen (again)

Question 18

Describe the anagen stage of the hair cycle:

Answer 18

growth phase - most follicles are in anagen

Question 19

Describe the catagen stage of the hair cycle:

Answer 19

transition phase, growth slows, atrophy of follicle

Question 20

Describe the telogen stage of the hair cycle:

Answer 20

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

Question 21

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

Answer 21

hair pushed out

Question 22

5 functions of hair?

Answer 22

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

Question 23

How can hair be useful for protection?

Answer 23

tough keratin hairs covering sensitive structures

Question 24

how can hairs help with thermoregulation?

Answer 24

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

Question 25

how can hairs help with communication/camouflage?

Answer 25

colours, arrector pili, glands opening into follicle

Question 26

How many epidermal layers do birds have?

Answer 26

2

Question 27

what are the two epidermal layers of the birds?

Answer 27

stratum germinativum (basale) stratum corneum

Question 28

how many glands do birds have?

Answer 28

only 3 - essentially glandless

Question 29

name the three glands a bird has:

Answer 29

uropygial (preen) gland aural gland vent gland

Question 30

what do developing feathers contain?

Answer 30

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

Question 31

difference between contour and down feathers:

Answer 31

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

Question 32

how many types of feathers are there?

Answer 32

6

Question 33

what is the rachis?

Answer 33

main shaft of the feather

Question 34

what is the calamus?

Answer 34

the base of the quill

Question 35

tactile hairs equivalent in birds are called?

Answer 35

bristle hairs - on faces of some birds

Question 36

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

Answer 36

powder down feathers

Question 37

describe the powder found in powder down feathers?

Answer 37

fine, waxy keratin powder

Question 38

what causes allergy to birds?

Answer 38

the powder found in powder down feathers

Question 39

how many layers does the reptile epidermis have? name them

Answer 39

3 stratum germinativum (=basale) stratum intermedium stratum corneum

Question 40

what are scales homologous to?

Answer 40

to hairs and feathers

Question 41

hairs, feathers, scales are all homologous meaning?

Answer 41

shared ancestry - all keratin structures from epidermis

Question 42

Why can reptiles risk thermal burns?

Answer 42

thick keratinised scales which reduce skin sensation

Question 43

what is ecdysis?

Answer 43

skin shedding

Question 44

what is skin shedding controlled by?

Answer 44

the thyroid gland

Question 45

what is dysecdysis?

Question 46

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

Answer 46

more susceptible to parasites, infection and medication overdose

Question 47

what happens to snakes when they are shedding?

Answer 47

they go blind - so have a behavioural change

Question 48

why do snakes go blind during shedding?

Answer 48

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

Question 49

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

Answer 49

lateral line system

Question 50

where are the tactile hairs found on a horse?

Answer 50

around the nares (nostrils), eyes and mouth

Question 51

What type of hair is the mane on a horse?

Answer 51

Guard hair

Question 52

Which cells determine skin and hair colouration?

Answer 52

melanocytes - in the basal layer of the epidermis. These melanocytes produce melanin granules that travel to the tips of the melanocyte cell, are pinched off and then phagocytosed by surrounding cells

Question 53

Where are the guard hairs mainly found on a sheep?

Answer 53

Face and legs

Question 54

Explain the difference between the coat of a horse and the coat of a domestic sheep?

Answer 54

Sheep barely have any guard (kemp) hairs, the coat of a sheep is generally less pigmented (fewer melanin granules from melanocytes) They have lost the ability to shed their spring coat

Question 55

Explain how we have to look after sheep differently to horses because of their coats?

Answer 55

Due to barely any guard hairs, sheep can get waterlogged in the rain They have to be shorn

Question 56

What forms the undercoat?

Answer 56

wool

Question 57

What forms the topcoat?

Answer 57

guard hairs

Question 58

What is the fleece in a sheep?

Answer 58

the guard hairs and the wool hairs together

Question 59

What are the guard hairs called in sheep?

Answer 59

kemp