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Tissues > Tissues 11- Hair and nails > Flashcards

Tissues 11- Hair and nails Flashcards

1
Q

What are the functions of hair

A

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

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2
Q

What do hairs and nails have in common

A

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

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3
Q

Name 2 places which don’t have hair

A

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

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4
Q

When do you start to grow hair

A

The 3rd trimester

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5
Q

What are the 3 types of hair

A

Lanugo
Vellus
Terminal

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6
Q

What constitutes the pilo sebaceous unit

A

hair follicle
hair shaft
errector pili muscle
sebaceous gland

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7
Q

Describe the different areas of the hair follicle

A

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)

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8
Q

Where is the hair shaft found

A

Above the scalp

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9
Q

What is the role of the hair bulb

A

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.

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10
Q

What is the role of the arrector pilli muscle

A

raise the hairs in shivering , to keep warm

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11
Q

What is the role of the sebaceous gland

A

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

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12
Q

Describe the arrector pilli muscle

A

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

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13
Q

Describe the hair follicle

A

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.

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14
Q

What does the hair shaft consist of

A

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

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15
Q

What cell types are found in the hair bulb

A

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

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16
Q

Describe the sebaceous glands

A

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.

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17
Q

Why do sebaceous glands appear clear

A

Due to their high lipid content.

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18
Q

Where is the hair shaft produced

A

In the hair bulb

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19
Q

Describe languo hair

A

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

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20
Q

Describe terminal hair

A

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.

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21
Q

Describe vellus hair

A

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

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22
Q

What is the pubic louse adapted to grip

A

Terminal hair

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23
Q

What are demodex mites

A

Commensal, native to the hair follicles of the nose

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24
Q

What diseases can head and body louse carry

A

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

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25
Q

Describe the cortex

A

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

26
Q

describe the medulla

A

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

27
Q

Describe the outer cuticle

A

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

28
Q

Describe how keratin filaments are formed

A

polypeptide, dimer, tetramer, profilament, filament

29
Q

What is the role of keratin

A

Forms strands contributing to strength, many different types

30
Q

What is the key difference between skin growth and hair growth

A

The skin grows continuously whereas the hair grows in cycles.

31
Q

Describe the anagen growth phase

A

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

32
Q

Describe the catagen growth phase

A

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.

33
Q

Describe the telogen growth phase

A

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.

34
Q

What happens between the growth phase stages

A

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

35
Q

Describe the differences in hair growth rate

A

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.

36
Q

Describe hair growth and synchronicity

A

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.

37
Q

Describe telogen effluvium

A

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

38
Q

Describe the underlying mechanism behind telogen effluvium

A

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

39
Q

describe the testosterone paradox

A

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

40
Q

Describe androgenic alopecia

A

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

41
Q

What scale is used to classify androgenic alopecia

A

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

42
Q

Describe Hirsutism

A 
Causes
Genetic variant
PCOS
Excess androgens
Drugs - Ciclosporin
43
Q

Describe alopecia areata

A

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.

44
Q

Describe folliculitis

A

Commonly caused by infection of the hair follicle

45
Q

Describe the roles of nails

A

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

46
Q

When does the nail start to grow

A

In the first 10 weeks

47
Q

Describe the basic structure of the nails

A

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

48
Q

Why are nails not as hard as claws

A

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

49
Q

Describe the anatomy of the nail

A

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

50
Q

Describe the nail matrix

A

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

51
Q

Is the lunula part of the matrix

A

Yes

52
Q

Describe nail growth

A

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
53
Q

Explain why toenails grow more slowly

A

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

54
Q

What produces the pink colour of the nail

A

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

55
Q

What is clubbing a sign of

A

CVD and lung cancer ( greater than 180 degree bend)

56
Q

Describe Beau lines

A

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

57
Q

Describe Koilonychia

A

Koilonychia (spoon shaped nails)

inherited, anaemia, hyperthyroid, drugs

58
Q

Describe psoriasis

A

1/3 patients will have nail involvement for psoriasis

Pitting
salmon spots
Onycholysis – distal and lateral separation of the nail

59
Q

Melanoma vs melanonychia strata

A

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.

60
Q

Describe systemic sclerosis

A

Giant capillaries
microhaemorrhages
Diagnosed by dermoscopy

61
Q

Why is the prognosis of melanoma in nails poor

A

Likely to spread- need to amputate

62
Q

Why is it difficult to take biopsies of nails

A

Unlikely to regrow

Tissues (12 decks)

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