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SUGER > Skin > Flashcards

Skin Flashcards

1
Q

What are the layers of the skin?

A
  1. Epidermis
  2. Dermis
  3. Subcutis
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2
Q

Which layers of the skin are waterproof?

A

Epidermis

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3
Q

Why does the skin wrinkle when wet?

A
  • mediated by sympathetic nervous system

- due to vasoconstriction in dermis

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4
Q

Explain the function of the skin as a physical barrier

A
  • structure of skin: resists trauma
  • stratified epithelium: resists abrasive forces
  • fat in subcutis: shock absorber
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5
Q

Explain vitamin D synthesis in the skin

A

7-dehydrocholestrol in plasma membranes of epidermal keratinocytes and dermal fibroblasts converted to previtamin D3 by UVB

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6
Q

Where is vitamin D stored in the skin?

A

Subcutis adipocytes

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7
Q

Which hormones act on the skin?

A

Androgens

Thyroid hormones

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8
Q

Where do androgens act in the skin?

A

Follicles

Sebaceous glands

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9
Q

Where do the thyroid hormones act on the skin?

A
  1. Keratinocytes
  2. Follicles
  3. Dermal fibroblasts
  4. Sebaceous glands
  5. Eccrine glands
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10
Q

What does skin colour depend on?

A
  1. Melanin
  2. Carotenoids
  3. Oxy/deoxyhaemoglobin
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11
Q

Describe melanin secretion

A

Synthesised in melanosomes within melanocytes from tyrosine

Transported via dendrites to adjacent keratinocytes

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12
Q

What are the functions of melanin?

A
  • skin colour

- scatters/filters UV light

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13
Q

What colours are:

  • Phenomelanin
  • Eumelanin
A
  • red/yellow

- brown/black

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14
Q

Does everyone have the same number of melanocytes?

A

Yes

Density varies between body cites

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15
Q

Does the skin contain more eumelanin or pheomelanin?

A

Eumelanin

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16
Q

Deleterious effects of melanin

A
  1. Prone to photodegradation (may generate ROS)
  2. Pheomelanin increases release of histamine
  3. Lots of melanin = less ale to utilise UV light to make vitamin D
17
Q

Skin response to sunlight

A
  1. Immediate pigment darkening
  2. Persistent pigment darkening
  3. Delayed tanning
18
Q

Explain immediate pigment darkening

A
  • photooxidation of existing melanin
  • redistribution of melanosomes
  • occurs within mins and lasts hours-days
19
Q

Explain persistent pigment darkening

A

(Tanning)

  • UVA&raquo_space; UVB
  • oxidation of melanin
  • occurs within hours
  • lasts 3-5 days
20
Q

Explain delayed tanning

A
  • increased melanin synthesis
  • occurs 2-3 days after UV exposure
    • maximal at 10-28 days
21
Q

Explain the skin’s barrier to infection

A

The properties that render the skin a barrier to water also help prevent infection

A range of peptides synthesised by granular-layer keratinocytes have antimicrobial properties

22
Q

Which cells in the epidermis contribute to the immune system?

A
  • Langerhans cells

- keratinocytes

23
Q

How do Langerhans cells contribute to the immune system

A
  • antigen-presenting cells

- secrete cytokines

24
Q

How to keratinocytes contribute to the immune system?

A

Secrete cytokines and chemokines

25
Q

Which cells in the dermis contribute to the immune system?

A
  1. Regulatory T cells
  2. Natural killer cells
  3. Dendritic cells
  4. Macrophages
  5. Mast cells
26
Q

What is the skin’s immune response?

A
  1. Langerhans cells migrate to dermis -> lymph nodes activate a T-cell response
  2. Keratinocytes proliferate and secrete cytokines
  3. Leucocytes enter skin from blood
27
Q

What are the sensory cells in the skin?

A
  1. Merkle cells
  2. Pacinian corpuscles
  3. Meissner corpuscles
  4. Myelinated & unmyelinated sensory nerve endings
28
Q

Where are the sensory cells in the skin found?

A

Dermis

Except Merkle cells - found in basal epidermis

29
Q

What do Merkle cells sense?

A

Light touch

30
Q

What do Pacinian corpuscles sense?

A

Pressure / vibration

31
Q

What do Meissner corpuscles sense?

A

Touch

32
Q

What do myelinated and unmyelinated sensory nerve endings in the skin sense?

A
  • pain
  • itch
  • temperature
33
Q

What is the insulating factor in the skin?

A

subcutaneous fat

34
Q

What prevents heat loss in the skin?

A
  1. Cutaneous blood flow
  2. Eccrine sweating
  3. Hair
35
Q

What is the equation for heat storage?

A

Heat storage = metabolism - work - evaporation +/- radiation +/- conduction +/- convection

36
Q

Describe autonomic regulation of the skin

A

Sympathetic alpha-noradrenergic: vasoconstriction

Sympathetic cholinergic: vasodilation

37
Q

Explain the mechanism of piloerection (goosebumps)

A
  1. Arrector pili muscles innervated by sympathetic alpha-adrenergic fibres
  2. Contraction raises cutaneous hairs
38
Q

What does subcutaneous fat in the skin act as?

A
  • insulator
  • shock absorber
  • energy store

SUGER (3 decks)

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