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1 SUGER > skin physiology and histology > Flashcards

skin physiology and histology Flashcards

1
Q

what 3 factors make the skin a waterproof barrier?

A
  1. keratin
  2. tight junctions
  3. lipids
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2
Q

what 3 factors make the skin a physical barrier to trauma?

A
  1. tight junctions in keratinocytes to resist frictional forces
  2. stratified epithelium resists abrasive forces
  3. fat in subcutis acts as shock absorber
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3
Q

what are the tissue resident macrophages in skin?

A

langerhans cells

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4
Q

what do langerhans cells do in an immune response?

A

= antigen presenting macrophages

  1. migrate from epidermis to dermis
  2. active a T cell response
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5
Q

what do keratinocytes do in an immune response?

A
  • proliferate

- secrete cytokines

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6
Q

what type of sensation do merkle cells respond to?

A

light touch

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7
Q

what are the 2 types of mechanoreceptors in the dermis? what sensations do they respond to?

A
  1. pacinian corpuscles → pressure/vibration

2. meissner corpuscles → touch

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8
Q

how is the skin an energy store?

A

subcutaneous fat
- acts as an insulator, shock absorber AND energy storer

white adipose connective tissue

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9
Q

how can UV affect skin?

A
  • burns
  • suppress action of langerhans cells
  • damage DNA (skin cancer)
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10
Q

which vitamin is produced and stored in the skin? In which layers?

A

vitamin D

  • produced In the superficial layers of the skin + stored In the deeper layers
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11
Q

How is Vitamin D synthesised?

A

UVB light

cleaves 7-dehydrocholestrol to pre vitamin D3 (cholecalciferol)

Vit D2 from supplements & D3 in diet

hydrolysed in liver into 25-hydroxy vitamin D (ie. calcifediol)

hydrolysed in kidney to 1,25 hydroxy vitamin D (ie. Calcitriol)

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12
Q

how is the skin involved in thermoregulation?

A

The amount of blood flow to the skin determines the degree of heat loss and, therefore, the core body temperature.

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13
Q

how many layers are there of the skin?

A

3

epidermis
dermis
subcutaneous tissue (fat)

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14
Q

what is the epidermis?

A
  • the outer layer of skin

- an epithelial layer resting on a BM made of type 4 collagen

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15
Q

what are the 4 layers of the epidermis?

A
  1. stratum corneum (outermost)
  2. stratum lucidum
  3. stratum granulosum
  4. stratum spinousum
  5. stratum basale (innermost)
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16
Q

what are the epidermal adnexae?

A
  • they are specialised down growths of the epidermis into the dermis
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17
Q

give 4 examples of epidermal adnexae structures?

A
  • hair follicles
  • sebaceous glands
  • eccrine sweat glands
  • apocrine sweat glands
18
Q

what are sebaceous glands?

A
  • accompany hair follicles in dermis

- produce sebaceous secretions which lubricate and waterproofs hairs via HOLOCRINE secretion

19
Q

what are eccrine sweat glands?

A
  • most common sweat glands
  • coiled tubes
  • in dermis
20
Q

what are apocrine sweat glands

A
  • specialised sweat glands found in groin, armpits, genitals, anus, external auditory canal (produce ear wax)
21
Q

describe the shape of the demo-epidermal junction?

A
  • ridged
  • has pegs
  • these act as anchors
22
Q

where is the subcutis layer of skin?

A

beneath the dermis

23
Q

where is melanin synthesised?

A

in the melanosomes of melanocyte cells

found in the stratum basale of the epidermis

24
Q

what are melanocytes derived from.?

A

melanocytes are derived from tyrosine

25
Q

what is the role of melanin?

A

absorbs UV (A&B) + protects from non-ionising radiation

26
Q

what is the distinguishing feature of the stratum corneum

A

acellular

27
Q

what is the distinguishing feature of the stratum granulsoum

A

where keratin forms

flattened squames

28
Q

what is the distinguishing feature of the stratum spinosum?

A

has keratinocytes

29
Q

what is the distinguishing feature of the stratum basale?

A

melanocytes and stem cells

so cell growth only in this layer

30
Q

when is more melanin produced?

A

when exposed to more UVB ie. tanning

31
Q

what is the purpose of the dermis layer?

what is it made of ?

A
  • made of gland and connective tissue (thick and elastic)

- allows for strength and flexibility

32
Q

what are the 2 different pigments produced by melanocytes?

A

black eumelanin

red pheomelanin

33
Q

what hormones are produced by skin?

A

IGF1 (insulin like growth factor)

vit D3 (actually a hormone)

34
Q

define emollients

A

trap moisture in skin allowing tit to rebuild

35
Q

define humectants

A
  • trap moisture and maintain low pH
36
Q

how is acne caused?

A

Hypercornification of skin: this blocks the hair follicle entrance
(ie. over build up of dead cells )

therefore the sebum (oily substance produced by the sebaceous glands ) gets trapped in the narrow hair cells

bacteria multiply in anaerobic conditions

cause irritation, inflammation and attract neutrophils

37
Q

what cells make up the skin barrier on the stratum corneum?

A

corneocytes - dead/termianted keratinocytes

38
Q

what are 3 components that make up the skin barrier?

A
  1. lipid lamellae - water barrier the tallows cells to swell
  2. NMF within corneocytes maintains low pH and regulates in/out of cell (water/allergens)
  3. corneodesmosomes - link corneocytes together
39
Q

what protein forms NMF?

A

profilaggrin to fillagrin reaction produces NMF

40
Q

what is desquamation?

A

when your skin peels as a result of shedding corneocytes

41
Q

why does desquamation happen?

A

degrading proteases

break down the corneodesmosomes that hold the corneocytes together

barrier breaks down

cells shed

42
Q

how is desquamation prevented?

A

proteases inhibitors

are used to prevent degrading proteases from breaking down the barrier

only work at low pH therefore important that pH5/5.5 is maintained by NMF

1 SUGER (9 decks)

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