Tissues 11- Hair and nails

Question 1

What are the functions of hair

Answer 1

Protection- Most obvious is protection – UV on the head (skin cancer on bald scalps)
- physical - eyelashes
- role depends on body location
Protects against minor trauma

Communication- sexual attraction, health, maturity

Sensation- Although hairs do not contain nerve fibres, hairs have sensory innervation in the follicles (hair shaft) which can amplify sensation. Hairs can also act as levers, amplifying movement.

Thermoregulation from an evolutionary perspective when man walked around naked– to some extent, practically speaking it doesn’t do much in man
2 aspects
Goosebumps when cold
Sweat evaporation more effectively from hair with the greater surface area, (evolutionary) - acts as lubricant for motion in areas like axilla, groin

Question 2

What do hairs and nails have in common

Answer 2

Protein (Keratin) product of the hair follicle (mini-organ) & nail matrix

Question 3

Name 2 places which don’t have hair

Answer 3

Everywhere except mucous membranes, palms and soles
- 5 million hairs on the body
- Only 5% on the scalp
(mouth, lips, eyes).

Question 4

When do you start to grow hair

Answer 4

The 3rd trimester

Question 5

What are the 3 types of hair

Answer 5

Lanugo
Vellus
Terminal

Question 6

What constitutes the pilo sebaceous unit

Answer 6

hair follicle
hair shaft
errector pili muscle
sebaceous gland

Question 7

Describe the different areas of the hair follicle

Answer 7

The follicle can be divided into 3 areas
Infundibulum – surface of skin to opening of the sebaceous glands. This is different because the epithelium is similar to the epidermis (granular layer and s.corneum) and desquamates into the lumen.

Isthmus – gland to insertion of arrector pilli muscle. The inner root sheath layer disintegrates in this level. Stem cells are thought to reside in the buldge (close to the muscle insertion) –important cells – daughter cells go to the bulb to form the shaft and inner root sheath.. Can also help in wound healing.

[suprbulbuar) – outer and inner root sheath. Inner moulds the shape of the hair fibre. Region of hair elongation and sheath production

Bulb- fed by blood from the dermal papilla.
Contains the matrix the produce the cells of the hair shaft and the inner root sheath. In pigmented hair, there are melanocytes – ( depositied in the cortex)

Dermal papilla – loop of capillary blood vessels in large cells and special fibroblast like cells. It is key in determining the type of hair follicle and maintainence of differentiation. It is androgen sensitive ( affect the size of the hair follicle)

Question 8

Where is the hair shaft found

Answer 8

Above the scalp

Question 9

What is the role of the hair bulb

Answer 9

Hair Bulb- where the hair grows from, sits in the mid/deep dermis, below the hair root. -the hair bulb is very complex interaction between vasculature and the hair.

Question 10

What is the role of the arrector pilli muscle

Answer 10

raise the hairs in shivering , to keep warm

Question 11

What is the role of the sebaceous gland

Answer 11

Makes sebum, lubricates the hair, prevents bacterial and fungal infections

Question 12

Describe the arrector pilli muscle

Answer 12

Smooth muscle under autonomic control is vestigial in humans, it contracts with cold, fear and emotion to erect the hair, produces goosebumps.

Question 13

Describe the hair follicle

Answer 13

The hair follicle is an invagination of the epidermis containing a hair. The portion above the site of entry of the sebaceous duct is the infundibulum.

Question 14

What does the hair shaft consist of

Answer 14

The outer cuticle that encloses a cortex of packed keratinocytes and an inner medulla (terminal hair).

Question 15

What cell types are found in the hair bulb

Answer 15

The germinative cells are found in the hair bulb, as are melanocytes which synthesise pigment.

Question 16

Describe the sebaceous glands

Answer 16

Sebaceous glands are found associated with the follicles, especially those of the chest, scalp and back. They are formed of epidermis derived cells and produce an oily sebum. The glands are small in children but become large and active during puberty, being sensitive to androgens. Serum is produced by holocrine secretion in which the cells disintegrate to release their lipid cytoplasm.

Question 17

Why do sebaceous glands appear clear

Answer 17

Due to their high lipid content.

Question 18

Where is the hair shaft produced

Answer 18

In the hair bulb

Question 19

Describe languo hair

Answer 19

Fine and long, formed in the fetus after 20 weeks. Normally shed before birth, but may be seen in premature babies. Also occur in anorexia. unpigmented, unmedullated

Question 20

Describe terminal hair

Answer 20

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

Question 21

Describe vellus hair

Answer 21

Short, fine, light coloured and cover most of the body. Unpigmented, unmedullated

Question 22

What is the pubic louse adapted to grip

Answer 22

Terminal hair

Question 23

What are demodex mites

Answer 23

Commensal, native to the hair follicles of the nose

Question 24

What diseases can head and body louse carry

Answer 24

Thyphus- common in war/tsunamis due to lack of sanitation

Question 25

Describe the cortex

Answer 25

the main structural component of the hair. Makes up the bulk of the fibre

Question 26

describe the medulla

Answer 26

Medulla – variable and may be absent. Tend to only present in larger fibres. Its has a spongy consistency made up of a mixture of proteins and air spaces

Question 27

Describe the outer cuticle

Answer 27

The hair is covered by an outer cuticle. This began as cells. – 5-10 overlapping cell layers – tile like in appearance. Progressively more keratin deposit – cells apoptose. Compact keratin associated with sulphur proteins (cysteine) disulphide bonds 14% in hair – corss links for strength. This is coated with long chain fatty acids. It acts to protect the hair physically and chemically.’waterproof’ This is called the hair fibre and is produced by the hair bulb

Question 28

Describe how keratin filaments are formed

Answer 28

polypeptide, dimer, tetramer, profilament, filament

Question 29

What is the role of keratin

Answer 29

Forms strands contributing to strength, many different types

Question 30

What is the key difference between skin growth and hair growth

Answer 30

The skin grows continuously whereas the hair grows in cycles.

Question 31

Describe the anagen growth phase

Answer 31

growth phase. Normally 85% hairs are in this stage. Energy intensive process, higly vascularized, most metabolically active - rate depends on the body site. Increased vasculature and VEGF expression

Question 32

Describe the catagen growth phase

Answer 32

Cell division slows and stops. The end of the shaft keratinizes and form a club shape. The dermal papilla and the club moves towards the base of the muscle insertion. Hair protein synthesis stops, the follicle retreats towards the surface.

Question 33

Describe the telogen growth phase

Answer 33

Hair is shed actively and the next anagen phase begins. The club hair can take 4-6 weeks to be released. This was originally thought to be passive. Now we know that the hair is actively shed from the follicle. Distinguished by presence of hair with a short club root.

Question 34

What happens between the growth phase stages

Answer 34

Between stages there is a complex diaglog with the vasculature locally and the dermis Communicaiton with the re-trigger of anaogen

Question 35

Describe the differences in hair growth rate

Answer 35

Rate of hair growth varies depending on site. For example, eyebrow hairs grow faster and has a shorter anagen phase than scalp hair. During the anagen phase – the max speed of growth varies with body site too. This is why hairs on different body sites have different lengths.

Question 36

Describe hair growth and synchronicity

Answer 36

Hair growth is randomised- but hair growth is synchronised during pregnancy. If all hair was synchronous- we would shed, this occurs post birth. After birth, due to external controls, hairs shift out of phase with each other.

Question 37

Describe telogen effluvium

Answer 37

Premature termination of anogen Telogen Diffuse Hair Loss ``` Many causes (trauma, stress, pregnancy,high fever Surgical trauma Sudden starvation Haemorrhage ? Emotional stress (lacking evidence) ) ``` Regrowth over 3-6 months

Question 38

Describe the underlying mechanism behind telogen effluvium

Answer 38

This is a condition loss of the club hairs. Premature termination of anogen. follicles are stimulated to leave anagen and enter telogen. If Acute telogen effluvium – They then shed 2-3 months later. More commonly Diffuse hair loss, never total

Question 39

describe the testosterone paradox

Answer 39

The mediators of the external influence tends to be hormonal. complex eg prolactin, oestrogens, melanin. The most interesting effects are with testerosterone on the hair follice. The effects are Referred to as the testosterone paradox. Lets take the example of what happens normally Prepubescent- most of the hair is vellus. During puberty there is a surge of testerone This leads to terminal hairs effected through androgen receptors The speed of effect depends of the follicle and body site Expalins why pubic and axillary hair grows 1st. Beard and chest hair come later – in response to the same level of testerone. – why and how is still poorly understood. At the other extremes of age- this same effect causes nose and ear hair to grow as you become old Lets look at what happens on the scalp. Already terminal hair. Androgen receptors – no action on the hair In balding areas. The scalp and hair look anatomically identical but effect exerting opposite effects The distribution of ‘androgen sensitive hair’ determines pattern of baldness as we get older. Seems to be an embrological developmental influence where these follicles are layed down. Seen on the scalp as Male pattern baldness Return to vellus follicles

Question 40

Describe androgenic alopecia

Answer 40

Androgen Sensitive 50% men over 50y >80% men over 70y Polygenic- 4 genes on X chromosome Treat with 5α reductase inhibitors/minoxidil distribution is different in women of androgen sensitive hairs Thinning of the hair from the centre

Question 41

What scale is used to classify androgenic alopecia

Answer 41

This is the Hamilton-Norwood scale for grading mamle patterned hair loss Ludwig scale for females

Question 42

Describe Hirsutism

Answer 42

``` Causes Genetic variant PCOS Excess androgens Drugs - Ciclosporin ```

Question 43

Describe alopecia areata

Answer 43

Hair loss is not all under hormonal control. Immune system Common. Affects 0.2% population Autoimmune attack of the hair follicle. Well circumscribed loss of hair Occurs quickly Assoicated with autoimmune conditions also Immune privileged status of anagen hair breaks down.

Question 44

Describe folliculitis

Answer 44

Commonly caused by infection of the hair follicle

Question 45

Describe the roles of nails

Answer 45

Protection (weapon) Chemical, physical, protects the distal fingertip, most sensitive part of the finger Touch Manual dexterity, facilitates grasping and tactile sensitivity Communication - socially In animals- can be used as weapon

Question 46

When does the nail start to grow

Answer 46

In the first 10 weeks

Question 47

Describe the basic structure of the nails

Answer 47

Mostly hard “hair” keratin (alpha keratin dense) Strong Longitudinal Ridging- protects against sheering forces Curvature- in 2 dimensions, across, and proximal to distal Strongly adherent to the nail bed

Question 48

Why are nails not as hard as claws

Answer 48

Not as hard as claws due to less calcium content & claws are beta pleated keratins

Question 49

Describe the anatomy of the nail

Answer 49

Vital part is germinal matrix –proximal, where the nail grows from -relative protection -extends back, horns Well protected 4-9mm in length. The distal end of the matrix is seen as the lunula – ½ moon. In most people can see onthe thumb. This area is critical to proper growth of the nail plate. If damaged it can lead to permanent nail deformities -look at the nail, there is a pale area proximally (more prominent on the thumbs) this is the matrix Shape of the lunala probably accounts for why the nail is round -Seals-Eponychium at the top Hyponychium at the bottom- thickened epidermis that underlies the free margin of the nail Leads to the onychodermal band – seal If compromised – infections in the nail

Question 50

Describe the nail matrix

Answer 50

Nail matrix consists of dividing cells which mature, keratinise and move forward to form the nail plate.

Question 51

Is the lunula part of the matrix

Answer 51

Yes

Question 52

Describe nail growth

Answer 52

Unique- grow out, not up. Because of adhesion and nail folds -growth at different rates between areas Nail surface is produced by the proximal nail bed. the nail plate consists of layers. The top of the nail is produced from the proximal most part of the nail matrix The matrix can also contain melanocytes.so this can be important if you suspect a melanoma Eg if the pigment is deep, it is from the distal matrix and excision is less likely to cause permanent damage Affected by may things - systemic disease, local disease, trauma e. g fractures

Question 53

Explain why toenails grow more slowly

Answer 53

The nail bed produces a smaller amount of keratin and is more adherent to the nail plate.

Question 54

What produces the pink colour of the nail

Answer 54

The adjacent dermal capillaries produce a small amount of pink colour of the nail

Question 55

What is clubbing a sign of

Answer 55

CVD and lung cancer ( greater than 180 degree bend)

Question 56

Describe Beau lines

Answer 56

Beau lines , described in 1836 seen in Typhoid patient survivors, and mumps but not TB

Question 57

Describe Koilonychia

Answer 57

Koilonychia (spoon shaped nails) | inherited, anaemia, hyperthyroid, drugs

Question 58

Describe psoriasis

Answer 58

1/3 patients will have nail involvement for psoriasis Pitting salmon spots Onycholysis – distal and lateral separation of the nail

Question 59

Melanoma vs melanonychia strata

Answer 59

Pigmentation in the nail. Can’t tell. All in the history The other is congenital - MELANONYCHIA STRIATA Seen in Hispanics and people of African and Asian decent.

Question 60

Describe systemic sclerosis

Answer 60

Giant capillaries microhaemorrhages Diagnosed by dermoscopy

Question 61

Why is the prognosis of melanoma in nails poor

Answer 61

Likely to spread- need to amputate

Question 62

Why is it difficult to take biopsies of nails

Answer 62

Unlikely to regrow