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Dermatology > Physiology > Flashcards

Physiology Flashcards

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Dermatology Board Prep flashcards
1
Q

What are skin appendages

A

Addition to the skin layers

Includes: hair follicles, melanocytes, glands etc

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2
Q

What are Blaschko’s lines

A

Show the developmental growth pattern of skin

Does not follow vessels or nerves

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3
Q

What can happen if there is a malformation in a Blaschko line

A

Disease can present in the segment that that line covers

Allows you to determine that the skin abnormality was developmental

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4
Q

What does the skin consist of

A

Epidermis = 5 layers
Dermo-epidermal junction
Dermis = connective tissue
Sub-cutis = mostly fat

Also appendages - nails, hair etc

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5
Q

What is the function of the dermis

A

Structural rigidity
Blood vessels, lymphatics, glands and follicles are found here
Also contains numerous nerve endings - sensory functions

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6
Q

Are the epidermal layers the same across the whole body

A

NO
They vary depending on functions
E.g. Thicker keratin layer on palms and soles
Differences in number of hair follicles and sweat glands

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7
Q

What controls epidermal turnover

A

Growth factors
Cell death
Hormones

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8
Q

What can occur if there is loss of control of epidermal turnover

A

Skin cancer

Psoriasis - cycle is accelerated

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9
Q

Describe the basal layer (stratum basal)

A

4th layer of epidermis Usually one cell thick
Small cuboidal cells
Lots of intermediate filaments
Highly metabolically active - divide all the time
Contains the Merkel Cells

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10
Q

Describe the prickle cell layer (stratum spinosum)

A

3rd layer of epidermis Large polyhedral cells
Lots of desmosomes - connections
Move up through layers erratically

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11
Q

Describe the structure of the granular layer

A 
2nd layer of epidermis 
2-3 layers of flatter cells 
Large granules containing structural filaggrin and protein 
Have lamellar bodies 
High lipid content 
Cell nuclei lost
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12
Q

What is the function of the granular layer

A

Goes on to form the ‘glue’ that seals the skin
The cells shrink and die, releasing their granules
Lipids and proteins released seal the skin

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13
Q

What is the function of the keratin layer

A

Forms a tight waterproof barrier

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14
Q

Describe the structure of the keratin layer (stratum corneum)

A

Made up of overlapping cell remnants - corneocytes
Cells have lost their nucleus and cytoplasm
80% keratin and filaggrin

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15
Q

What causes warts

A

Infection that affects the keratinocytes
Viruses infect the cells and cause increased proliferation
Tries to push infected cells out but just forms a thickened layer on top = wart

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16
Q

What is the function of melanocytes

A

Creates melanin pigment by converting tyrosine - occurs in melanosomes
This absorbs light so works as a natural sun protection
Forms a cap over the nucleus to protect DNA

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17
Q

Describe the structure of melanocytes

A

Have long dendrites
Forms synapses with the basal layer to produce pigment
Found in the keratin layer

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18
Q

What causes melanin to be produced

A

Exposure to UV light

Hormones

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19
Q

What causes vitiligo

A

T cells attack melanocytes
Causes loss of pigmentation
Autoimmune condition

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20
Q

What is albinism

A

Genetic condition

Melanocytes don’t produce pigment

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21
Q

What is Nelson’s syndrome

A

A disorder where melanin stimulating hormone is produced in excess by the pituitary gland
Causes hyperpigmentation
Sometimes occurs as result of a tumour

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22
Q

What is a tumour of the melanocytes called

A

Melanoma

Malignant

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23
Q

What is the function of Langerhan’s cells

A

Part of skin immune system
Pick up antigens in skin and transport them to the lymph nodes
Act as antigen presenters

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24
Q

Describe Merkel cell cancer

A

Malignant transformation of the merkel cells

Very dangerous cancer with high mortality - 90%

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25
Q

Describe the structure of a pilosebaceous unit

A

Has an epidermal component plus dermal papilla
Contains specialised keratins
Has an adjacent sebaceous gland - moisturises skin
Melanocytes above papilla give hair colour

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26
Q

Which hormones can influence hair growth

A

Androgens

Thyroxine

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27
Q

What is Virilisation

A

Excess hair growth in male pattern due to excess androgen

May be due to an androgen-producing tumour

28
Q

What is alopecia areata

A

Autoimmune condition where T lymphocytes attacks the hair follicle
Causes hair loss

29
Q

Describe the structure of the nails

A

Contains specialised keratins
Come from specially differentiated skin cells
Nail plate of hard keratin sits on nail bed
Matrix contains dividing cells which grow the nails
Firm and rigid
If bed is damaged it is often irreversible and the nail will continue to grow in a abnormal way

30
Q

What can happen if the DEJ fails

A

The skin can slip, split and blister

31
Q

What is Bullous Pemphigoid

A

A skin condition where antibodies form against parts of the dermo-epidermal junction
Causes large blisters
Seen in elderly patients

32
Q

What is epidermolysis bullosa

A

A genetic condition caused by a mutation in one of the proteins of the DEJ
Skin is extremely fragile and blisters/falls off easily
Can be life threatening

33
Q

What makes up the dermis

A

Ground substance
Cells: mainly fibroblasts (connective tissue), macrophages, mast cells, lymphocytes and langerhans cells
Fibres: collagen and elastin - given tensile strength and elasticity
Muscles, blood vessels, lymphatic system and nerves

34
Q

Describe the fibres found in the dermis

A

Most are collagen which provides strength and support
Elastin provides skin elasticity
Becomes less functional as we age

35
Q

What is photo ageing

A

Exposure to UV light can attack the fibres in the dermis and cause ageing - more wrinkles etc
Smoking can also have this effect

36
Q

Why does the skin have more blood supply than necessary

A

Partly due to role in thermoregulation - arteriovenous anastomoses are particularly important in this

37
Q

What is an angioma

A

Benign overgrowth of blood vessels

Presents as large purple patches

38
Q

Describe the nerves within the skin

A

Somatic sensory

  • free nerve ending for pain and heat
  • Pacinian (pressure) receptors
  • Meissners (vibration) corpuscles

Autonomic nerves
- for blood vessels, nerves and glands

39
Q

What is the function of the sebaceous gland

A

Lubricate and moisturise hair and skin

May offer immune protection by preventing bacteria from entering the follicle

40
Q

What can cause acne

A

Overproduction of sebum by sebaceous glands
Blocks the pores
Occurs during puberty due to hormones

41
Q

Describe apocrine sweat glands

A

Part of pilosebaceous unit - open into hair follicle
Activated during puberty - androgen dependent
Produce oily fluid that starts to smell
Found in axillae, nipple and genitals

42
Q

What is the function of eccrine sweat glands

A

Produce sweat to cool us down - regulate heat and salt loss
Moistens palms
On the soles they improve grip

43
Q

Where are eccrine glands found

A

Over the whole body
Axilla palms and soles in particular
Not in lips and genitals

44
Q

What are the functions of the skin

A 
Barrier 
Metabolism and detoxification 
Fluid balance
Thermoregulation 
Immune defense 
Communication - sensory function
45
Q

What is toxic epidermal necrolysis

A

Drug causes failure of cohesion between the epidermis and dermis - usually across 90% of the body
Increases infection risk, pain, loss of moisture and protein

46
Q

What does the skin act as a barrier against

A

Friction, mechanical trauma, UV
Irritants, allergens, toxins
Bacteria, viruses, fungi

47
Q

What is the function of vitamin D

A

Calcium absorption

48
Q

What can vitamin D deficiency cause

A

Rickets in children

Osteoporosis in the elderly

49
Q

How does the skin help with thermoregulation

A

Has thermoreceptors
This will induce behavioural changes
Blood vessels dilate or constrict to control heat
Sweating cools us down

50
Q

How does the skin act in immune defence

A

Langerhan’s and T cells are important

An intact dermis & epidermis are key

51
Q

What are the sensory functions of the skin

A

Touch, pressure and vibration
Pain and itch
Temperature

52
Q

The epidermis is composed primarily of which cell type

A

Keratinocytes

53
Q

Where are keratinocytes produced

A

In the basal layer of the epidermis

They then undergo a process of migration starting from the basal layer, upwards to the stratum corneum

54
Q

What are the 5 layers of the epidermis from top to bottom

A 
Stratum corneum 
Stratum lucidum 
Stratum granulosum
Stratum spinosum 
Stratum basal
55
Q

What are the two main layers of the dermis

A

Papillary dermis - loose CT and lots of cells

Reticular dermis - denser CT and fewer cells

56
Q

Do people with darker skin tones have more melanocytes

A

No - we all have the same number

Darker skin has larger melanosomes containing more melanin and the melanosomes degrade slowly compared to fair skin

57
Q

How does the keratin layer differ in dark skin

A

Keratin layer in darker skin tones is more compact

58
Q

Why are those with darker skin at higher risk of keloid scars

A

Larger and more numerous fibroblasts

The higher fibroblast activity increases keloid risk

59
Q

List the 3 phases of the hair cycle

A

Anagen – growth phase, 2-7years, most hairs in this phase 85%
Catagen – transitional stage, 2 weeks, hair detaches from the blood supply
Telogen - approx 3 months, hair falls out, ‘released from the follicle’ and new hair grows behind it

60
Q

Which parts of the body lack sebaceous glands

A

Palms and soles

61
Q

Name the muscles associated with hair follicles

A

Arrector pili

Can pull the hair perpendicular to the skin during cold / fright ( goose bumps)

62
Q

Meissener’s corpuscles detect what

A

Tactile sensation

Found in dermis

63
Q

Pacinian corpuscles detect what

A

Deep pressure

Found in dermis

64
Q

What is primary intention healing

A

When the edges of a wound are brought together - leads to rapid healing
Usually with stitches etc

65
Q

What is healing by secondary intention

A

Wound is left open and heals from the bottom up
Inflammation then granulation then tissue remodelling
Used for for larger wounds that are too tight to stitch, or areas where direct closure would cause significant distortion

66
Q

Describe the different degrees of burn

A

First degree: epidermis only.
Second degree/Partial thickness: epidermis and dermis.
Third degree/ Full thickness: extends beyond dermis

Dermatology (14 decks)

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