ANATOMY (Hair/SpecializedCells)

Question 1

hair

Answer 1

-elongated keratinized structures that form within epidermal invaginations (hair follicles)
-derived form epidermis, but extend deep into dermis
-grows discontinuously: periods of growth followed by periods of rest

Question 2

Components of a hair

Answer 2

-follicle
-hair root
-shaft

Question 3

follicle

Answer 3

-epidermal part

Question 4

hair root

Answer 4

-embedded in dermis part
Ex. white part when we pull out hair

Question 5

shaft

Answer 5

-outside the skin (extending beyond the surface)
-3 components

Question 6

components of the shaft

Answer 6

-medulla
-cortex
-cuticle

Question 7

a developing hair

Answer 7

1. Anagen
2. Catagen
3. Telogen

Question 8

anagen

Answer 8

-growth period
-dermal papilla

Question 9

catagen

Answer 9

-stops growing (club root)

Question 10

telogen

Answer 10

-long period of time
-not growing: ‘holding’ it’s position
-just embedded in skin

Question 11

Hair bulb:

Answer 11

-terminal dilation of the growing hair follicle
-dermal papilla inserts into base of hair bulb and contains a capillary network required to sustain the hair follicle

Question 12

Dermal papilla (hair bulb):

Answer 12

-covered by keratinocytes continuous with those of the basal epidermis
*forms the matrix of the elongating hair roots

Question 13

Keratinocytes of hair bulb:

Answer 13

-divide rapidly around the dermal papilla and undergo keratinization, melanin accumulation and terminal differentiation
-differentiate into variable amounts and type of keratin

Question 14

Thick hairs (hair root)

Answer 14

-large keratinized cells form the central medulla
-heavily keratinized and densely packed cells make up cortex around the medulla
-most peripheral cells comprise the cuticle (think layer of heavily keratinized, squamous cells covering the cortex)

Question 15

Hair follicle:

Answer 15

-internal epithelial root sheath
-external epithelial root sheath
-connective tissue sheat
-dermal papilla

Question 16

Arrector pilli muscles:

Answer 16

-smooth muscles (we can’t control them(
-temperature ‘control’
>hair pulled straight when cold

Question 17

2 patterns of hair cycle/growth:

Answer 17

-continuously grow
-majority of hair grows and then stops and stays in that state

Question 18

Hair types:

Answer 18

-guard hair (air trapped allowing animal to stay warm)
-under-fur (wool)
-tactile (ex. whiskers)

Question 19

In most animals, fetal state: hair growth:

Answer 19

-primary hair starts from follicle
-a secondary hair will grow from the same follicle
-primary hair will have glands opening into it

Question 20

Hair pattern of pig:

Answer 20

-hair follicles in groups of 3

Question 21

Hair pattern of the dog:

Answer 21

-all pointing in one direction
-three grouped follicles
>secondary are thinner
>primary are thicker

Question 22

Hair pattern of cat:

Answer 22

-one big primary
-get 3 smaller primaries
>each get 9 secondaries

Question 23

Primary hairs:

Answer 23

-usually guard hairs
-from primary follicles
-associated with skin glands
-develop first

Question 24

Secondary hairs:

Answer 24

-usually underfur/wool
-from secondary follicles
-not associated with skin glands
-develop later

Question 25

Fibre producing species:

Answer 25

*economic importance is the under-fur
-wool
-cashmere and mohair
-alpaca and vicuna
-qiviut, etc.
*from secondary follicles
*selective breeding to increase the ratio of secondary to primary fibers

Question 26

Under-fur:

Answer 26

-usually from secondary follicles
>no sweat glands
-grow continuously, must shear each year
Ex. Australian Merino

Question 27

Guard hairs:

Answer 27

-usually from primary follicles
>sweat glands
-more for milk and meat
Ex. Karayaka

Question 28

Whiskers:

Answer 28

-associated with blood sinus and Pacinian corpuscles
>blood sinus: feels vibrations and amplify them
>many free nerve endings
-protrude beyond the neighbouring guard hair
-lip, chin, cheeks and above eyelids

Question 29

Tylotrich guard hair:

Answer 29

-little larger than normal hairs
-spread all over skin
*between hair and whiskers
-smaller follicle of blood sinus than wiskers
>have tactile elevations

Question 30

Tactile elevations:

Answer 30

-where hair exits from the skin
-raised part of epidermis that has nerve endings
-cats and dogs have them (usually associated with tylotrich guard hair)