Chapter 1- Hair Cycle

Question 1

Name the phases of hair growth

Answer 1

1. anagen (Growth) 2. catagen (regression) 3. telogen (rest) 4. exogen (shedding)

Question 2

Growth phase is AKA

Answer 2

anagen

Question 3

Regression phase is AKA

Answer 3

catagen

Question 4

Rest phase is AKA

Answer 4

telogen

Question 5

Shedding phase is AKA

Answer 5

exogen

Question 6

Hair cyclic activity primarily involves what portion of the hair follicle?

Answer 6

The lower (inferior) region that is below the insertion of the arrector pili muscle

Question 7

Name the two portions of the hair follicle and their relative locations

Answer 7

1. upper portion- “permanent” portion 2. lower (inferior) region

Question 8

Which portion of the hair follicle undergoes dramatic changes involving apoptosis and later regeneration?

Answer 8

lower (inferior) region

Question 9

Hair growth cycles involve the repeated induction of hair follicle _____(phase of hair cycle) with concurrent ____(direction) growth through the dermis.

Answer 9

anagen; downward

Question 10

Catagen is the transitional period between which stages of hair cycle?

Answer 10

anagen and telogen

Question 11

The hair cycle (and thus the hair coat) are controlled by what things?

Answer 11

1. photoperiod 2. ambient temperature 3. nutrition 4. hormones 5. general state of health 5. genetics 6. poorly understood intrinsic factors

Question 12

Intrinsic factors that influence the hair cycle include what cells and structures?

Answer 12

growth factors and cytokines produced by the follicle, the dermal papilla, and other cells (lymphocytes, macrophages, fibroblasts, mast cells) in the immediate environment

Question 13

Hair replacement in dogs and cat is in what kind of pattern?

Answer 13

mosaic

Question 14

Does hairgrowth respond predominantly to ambient temperature or to photoperiod?

Answer 14

photoperiod

Question 15

How long does hair grow?

Answer 15

Until it reaches its preordained length

Question 16

Under conditions of ill health, what hair cycle phase may be shortened?

Answer 16

anagen

Question 17

Are anagen or telogen hairs more easily lost?

Answer 17

telogen

Question 18

Why do animals who are systemically ill shed excessively?

Answer 18

More hairs are in telogen, and those hairs are more easily lost

Question 19

What two hormones accelerate hair growth?

Answer 19

thyroid and growth hormones

Question 20

What substances inhibit anagen and suppress hair growth rate?

Answer 20

glucocorticoids, estrogens

Question 21

What cells play a fundamental role in the induction of epithelial differentiation?

Answer 21

dermal papilla cells, a mesenchymal component of the hair bulb

Question 22

Alterations in factors controlling the hair follicle cycle results in what abnormality?

Answer 22

follicular atrophy

Question 23

Alterations in factors controlling hair follicle structure results in what abnormality?

Answer 23

follicular dysplasia

Question 24

How long does it usually take for normal or short coat to regrow following shaving?

Answer 24

3 to 4 months

Question 25

How long for long coats to regrow after shaving?

Answer 25

As long as 18 months

Question 26

How long does it take for follicular arrest to disappear (following shaving for surgery)

Answer 26

6 months to 2 years after clipping