Structure and Function of the Hair

Question 1

function of eyelashes

Answer 1

prevent dust from entering eyes, shades eyes from sunlight

Question 2

function of nose hair

Answer 2

filter air entering the nostrils

Question 3

function of scalp hair

Answer 3

retain body heat–50% of body heat is lost through the head

Question 4

function of body hair

Answer 4

protects against friction

Question 5

name the 3 stages of the hair growth cycle

Answer 5

1. Anagen
2. Catagen
3. Telogen

*remember ACT!

Question 6

describe the anagen stage of the hair growth cycle

Answer 6

growth stage where new hairs are produced

-nutrition comes from the dermal papilla
-hair bulb is active: pushes down into the dermis and expands through cell mitosis

Question 7

describe the catagen stage of hair growth

Answer 7

regression or “falling out” stage of hair growth

-hair shaft grows upward and detaches from the bulb, dermal papilla collapses

Question 8

describe the telogen stage of hair growth

Answer 8

resting stage of growth, hair is at its full size and showing above the skin surface

-hair bulb is inactive and the hair falls out
-bulb moves up into the dermis and a new hair starts to grow

Question 9

how long does it take for the hair to complete its growth cycle?

Answer 9

4-13 weeks

Question 10

name the parts of the hair structure + their functions

*study diagram on pg 12 of manual

Answer 10

-hair follicle: pore-like indentations of the skin from which the hair grows

-root: the portion of the hair that lies in the follicle

-shaft: the portion of the hair above the surface

-bulb: the enlarged base of the root

-papilla: contains a blood supply and other elements essential for hair growth

-arrector pili muscle: involuntary muscle attached at an angle to the base of the follicle, causes goosebumps

-sebaceous gland: the source of new hairs

Question 11

what are the 3 parts of the hair strand?

Answer 11

1. medulla
2. cortex
3. cuticle

Question 12

describe the medulla

Answer 12

-central innermost layer of the hair comprised of loosely connected keratinized cells
-determines hair texture

Question 13

describe the cortex

Answer 13

-constitutes the mass of most hairs, determines the strength and hair colour
-consists of elongated keratinized cells cemented together
-melanin granules aligned longitudinally (vertically) in the cells of the cortex

Question 14

describe the cuticle

Answer 14

-outermost layer made up of a single layer of “scales” which overlap like shingles leading toward the tip of the hair
-“scales” are translucent and colourless
-protects the cortex, gives hair elasticity

Question 15

describe lanugo hair

Answer 15

soft hair found on fetuses that sheds after birth and is replaced with either vellus or terminal hair

Question 16

describe vellus hair

Answer 16

-replaces lanugo hair after birth
-found everywhere except palms, soles, eyelids, lips, nipples and navel
-very fine and soft, “peach fuzz”

Question 17

describe terminal hair

Answer 17

dark, coarse hair found on the head, brows and pubic area

*during puberty, follicles are naturally regulated to switch from producing vellus hairs to producing terminal hairs in these areas