9 Hair and Nails

Question 1

*Q: What are the 4 functions of hair?

Answer 1

A: protection (not much but some against injury, UV //+eyelashes and eyebrows)

sensation (hair fibres have lots of nerve fibres around them)

thermoregulation (less for humans but we do have pili erector muscles)

communication (eg sexual communication)

Question 2

Q: What do hair and nails have in common?

Answer 2

A: protein (keratin)= product of the hair follicle (mini organ) and nail matrix

keratin provides structure and substance

Question 3

Q: Name 2 places that don’t have hair?

Answer 3

A: palms/soles and mucous membranes

Question 4

Q: When do humans grow hair?

Answer 4

A: 3rd trimester in utero

Question 5

*Q: Describe the structure of a pilo sebaceous unit. Label a diagram. (5)

Answer 5

A: (what we usually describe as hair)
hair follicle is an invagination of the epidermis with hair shaft growing out from it and hair bulb at bottom where it actually grows from

• hair follicle
• hair shaft
• erector pili muscle
• sebaceous gland

infundibulum (sebaceous gland and up)
isthmus (bulb up)
(suprabulbar)
hair bulb/inferior segment-> contains germative cells and melanocytes that synthesise pigment

Question 6

*Q: What are the 3 main types of hair? Describe

Answer 6

A: -lanugo (fine and downy and developed in utero)

• vellus (short and downy and thin and on body and face)
• terminal (thick and pigmented and on scalp, pubic area, eyebrows, lashes, beard)

Question 7

Q: What do we all have lining our follicles? Dangerous?

Answer 7

A: -demodex mite
-harmless mostly

(short arms)

Question 8

*Q: What is the structure of hair? (cross section) Pigment? Include rough sketch.

Answer 8

A: -medulla in centre

• surrounded by cortex packed of keratinocytes
• outer cuticle

terminal hair has pigemented medulla

rounded then longitudinal around and flakes around

Question 9

Q: Describe the structure of keratin filaments.

Answer 9

A: polypeptide -> dimer -> tetramer -> protofilament -> filament

Two dimers line up head-to-tail in a staggered fashion to form a tetramer

Numerous tetramers line up end to end to make a protofilament

Question 10

Q: What is the structure from keratin to cuticle of hair?

Answer 10

A: keratin type I or II -> intermediate filament -> matrix -> macrofibril -> cortical cell -> cortex -> cuticle

Question 11

*Q: Name the phases of hair growth. Describe.

Answer 11

A: -anagen= growing phase (at any one time 80/90% scalp hairs are in this phase)

• catagen= resting phase (10-20)
• tetogen= shedding phase (1%)

(grows and drops out to be replaced by another)

Question 12

Q: What determines hair length?

Answer 12

A: length of anogen phase and how fast hair grows

Question 13

Q: What’s the rate of hair growth for beards?

Answer 13

A: 0.27 mm/day

Question 14

Q: Describe the concept of synchronicity.

Answer 14

A: all hairs when a baby is born grow in sync (to certain degree)

post birth-> loses synchronicity -> fall out in random pattern

Question 15

Q: What is telogen effluvium? (5)

Answer 15

A: -condition that causes hair loss

• all hairs go back in synchronicity and fall out in sync
• premature termination of anogen -> telogen
• causes include illness and stress
• regrow over 3-6 months

Question 16

Q: What is the testosterone paradox?

Answer 16

A: vellus hairs and those on body are genetically programmed to (under the influence of androgens) turn into terminal ones

at puberty hairs in the pubic region (and in men, beard area) etc will become thicker = terminal hairs

over many cycles

BUT hairs on head will undergo miniaturisation in certain areas eg on a mans scalp top-> undergo progressive miniaturisation with progressive hair cycles until the hair is so small it disappears and follicles scar up

=> called in a man: androgenic alopecia

similar condition can affect women where androgen exposure can be a factor

Question 17

Q: How many men are affected by androgenic alopecia? Cause? Treatment?

Answer 17

A: 50% over 50yrs
>80% over 70yrs

polygenic

5 alpha reductase inhibitor/minoxidil (work to certain extent)

Question 18

*Q: What are the 3 functions of nails?

Answer 18

A: -protection (weapon; chemical and physical): grip

• touch: manual dexterity (hard keratin)
• communication: socially

Question 19

*Q: What are nails made of? Why are they strong?

Answer 19

A: mainly hard keratin

longitudinal ridges and curvature

Question 20

*Q: Describe nail anatomy using a diagram. (7)

Answer 20

A: -inside (the bone)= distal phalanx

• nail plate above hyponychium (=thickened epidermis that underlies the free margin of the nail)
• end of nail plate is germinal matrix (just under skin)
• eponychium is skin just on top
• lunula is white bit at bottom = visible part of the matrix
• onychodermal band= white tip

Question 21

*Q: Describe the growth of the nail plate.

Answer 21

A: nail plate in made in germinal matrix and grows across nail bed-> move and keratinize

Question 22

*Q: What’s the rate of nail growth on fingers? Toes? What is the thickness of the nail plate?

Answer 22

A: 3mm /month
1mm /month

0.3-0.5 mm

Question 23

*Q: What causes the contraction of the erector pili muscles in humans? (3)

Answer 23

A: cold, fear, emotion

Question 24

*Q: What are sebaceous glands associated with? where? (3) Formed from? Function? Overtime?

Answer 24

A: follicles

esp those of the scalp face chest and back

epidermis derived cells

oily sebum: produced by holocrine secretion in which cells disintegrate to release their lipid cytoplasm

small in children but large and active during puberty-> being sensitive to androgens

Question 25

Q: What causes the pink of the nail?

Answer 25

A: adjacent dermal capillaries

Question 26

*Q: What is Hirsutism? causes? (4)

Answer 26

A: condition of unwanted, male-pattern hair growth in women

Genetic variant
PCOS
Excess androgens
Drugs - Ciclosporin

Question 27

Q: Describe androgenic alopecia in women. (3)

Answer 27

A: distribution is different in women of androgen sensitive hairs
Thinning of the hair from the centre
Ludwig scale