11. Hair and Nails

Question 1

Function of hair

Answer 1

Protection (against UV damage)
Sensation (sensory innervation within follicles which can amplify sensation)
Thermoregulation (minimal in humans)
Communication

Question 2

What are hair and nails comprised of?

Answer 2

Keratin

Products of hair follicle and nail matrix (respectively)

Question 3

Where is hair?

Answer 3

Everywhere except mucous membranes, palms and soles

Only 5% of hair is on scalp

Question 4

When does hair start growing?

Answer 4

3rd Trimester in utero

Question 5

What is the pilo sebaceous unit comprised of?

Answer 5

Hair follicle
Hair shaft
Arrector pili muscle
Sebaceous gland

Question 6

What is a hair follicle?

Answer 6

Invagination of epidermis containing a hair

Question 7

What is the hair shaft comprised of?

Answer 7

Outer cuticle that encloses a cortex of packed keratinocytes

+ An inner medulla (in terminal hairs)

Question 8

Where are germinative cells and melanocytes found?

Answer 8

In hair bulb

Question 9

Arrector pilli muscle (autonomic control) is vestigal in humans

Answer 9

Contracts with cold, fear and emotion

To erect hair, produces goose pimples

Question 10

Where are sebaceous glands found?

Answer 10

Associated with follicles, especially those of the scalp, face, chest and back

Question 11

What are sebaceous glands formed of and what do they produce?

Answer 11

Formed of epidermis derived cells

Produce an oily sebum

Question 12

When do sebaceous glands become large and active?

Answer 12

At puberty

As sensitive to Androgens

Question 13

How is Sebum produced?

Answer 13

By holocrine secretion

In which cells disintegrate to release their lipid cytoplasm

Question 14

Name the 3 types of hair

Answer 14

Lanugo
Vellus
Terminal

Question 15

Describe Lanugo hair

Answer 15

Fine and long
Formed in fetus at 20 weeks.
Normally shed before birth but may be seen in premature babies
Occur in anorexia.

Question 16

Describe Vellus hair

Answer 16

Short, fine and light coloured

Cover most of body

Question 17

Describe Terminal hair

Answer 17

Longer, thicker and darker.
Found on scalp, eyebrows, eyelashes, and pubic, axillary and beard areas.
Originate as a vellus hair, differentiation is stimulated at puberty by androgens.

Question 18

Pubic Louse

Answer 18

Adapted to grip terminal hair
Related to gorilla louse
Eyelashes – site for pubic louse attachment

Question 19

Head lice and body lice are genetically different

Answer 19

Head lice only target hair on head - do not carry disease

Body lice can carry disease and do not target hair on head

Question 20

Demodex mite

Answer 20

lives inside hair follicle of everyone,

not harmful

Question 21

What is the only type of hair that a medulla is found in?

Answer 21

Terminal

Question 22

How are hair fibres composed?

Answer 22

Keratin protein forms filaments which are supercoiled to form larger filaments, grouped/ linked together to form strong strands

Question 23

Genetic defects in keratin

Answer 23

causes genetic syndromes with effects on hair, skin and nails

Question 24

The Hair cycle

Answer 24

Anagen- Growing phase
Catagen- Resting phase, stops growing
Telogen- Sheds

Question 25

Different hairs in different locations have different

Answer 25

Anagen length | determines maximum length of hair

Question 26

Synchronicity of hair

Answer 26

Hair in synchronicity at birth All hairs synchronise, Leading to complete hair loss at 3 months

Question 27

What is the normal synchronicity of hair?

Answer 27

normal for all hairs to asynchronous | Occurs after birth

Question 28

Telogen effluvium

Answer 28

``` A cause of hair loss All hairs become synchronous again Premature termination of Anagen -->Telogen Diffuse Hair Loss Many causes e.g. stress Regrowth over 3-6 months ```

Question 29

Testosterone Paradox

Answer 29

Hairs become thicker & pigmented Androgens cause vellus follicle to become terminal follicle Occurs on scalp of men (androgen sensitive area- Androgenic alopecia) Causes hair to undergo miniaturisation

Question 30

Miniturisation of hair

Answer 30

Each cycle hair becomes slightly smaller until it is wispy | and no follicle is left

Question 31

Female pattern alopecia

Answer 31

hair thinning on top of head, but side preserved | androgens have a smaller role as more complex

Question 32

Hirsutism

Answer 32

Hairy, in male patterned distribution (when it should not be) e.g. beard e.g. In females / children caused by excessive androgen drive e.g. By PCOS, Drugs, Excess androgens

Question 33

Alopecia Areata

Answer 33

autoimmune condition | Immune privileged state of anagen stops, leading to patchy hair loss

Question 34

Folliculitis

Answer 34

Inflammation of follicles e.g. acne

Question 35

Function of nails

Answer 35

``` Protection (weapon) – Chemical, physical Touch – Manual dexterity Communication – socially ```

Question 36

Structure of nails

Answer 36

Mostly hard “hair” keratin Strong: – Longitudinal Ridging – Curvature

Question 37

What does nail matrix contain?

Answer 37

Dividing cells which mature, keratinize and move forward to form nail plate

Question 38

Thickness and growth rate of nail plate

Answer 38

Thickness: 0.3-0.5mm | Growth rate: 0.1mm /day (finger nail)

Question 39

What produces the small amount of pink colour of nails?

Answer 39

Adjacent dermal capillaries

Question 40

What is the visible part of the nail matrix?

Answer 40

White lunula

Question 41

What is the Hyponychium of a nail?

Answer 41

Thickened epidermis that underlies the free margin of the nail.

Question 42

What is the nail surface produced by?

Answer 42

Proximal nail bed

Question 43

Clubbing

Answer 43

Tip of fingers swollen Nail is distorted >180 degrees Many disorders cause clubbing e.g. Lung cancer

Question 44

Beau’s Lines

Answer 44

Systemic illness or severe trauma causes ridge in nail

Question 45

Koilonychia

Answer 45

spoon shaped nails | inherited, can indicate iron deficiency anaemia, hyperthyroid, drugs

Question 46

Psoriasis

Answer 46

Pitting in nail Salmon spots- psoriatic plaques visible under nail Onycholysis- nail plate splits away from nail bed

Question 47

Yellow nail syndrome

Answer 47

Rare | Onset 40-50 with lung/sinus disease

Question 48

Nail Pigmentation

Answer 48

Melanonychia Striata or Melanoma | Streaks indicates something in nail matrix is making pigment

Question 49

Systemic sclerosis

Answer 49

Giant capillaries | Microhaemorrhages

Question 50

Dermoscopy finding disrupted/ irregular/ thrombosed hairpin vessels on nail cuticle

Answer 50

sign of Systemic Sclerosis