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dermatology > structure and function of the skin > Flashcards

structure and function of the skin Flashcards

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Dermatology Board Prep flashcards
1
Q

what are the 3 main layer of the skin

A
  • epidermis
  • dermis
  • subcutis
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2
Q

what are some functions of the skin

A
  • physical barrier against friction and shearing forces
  • protection against infection, chemicals, UV radiation
  • synthesis of vitamin D
  • temperature regulation
  • sensation
  • antigen presenting and wound healing
  • hormonal synthesis
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3
Q

what kind of epithelium is the epidermis

A

stratified squamous epithelium

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4
Q

what are the downward projections of epidermis into the dermis called

A

rete ridges

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5
Q

what is epidermis mainly composed of

A

keratinocytes

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6
Q

where do keratinocytes originate

A

from basal layer

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7
Q

when do keratinocytes differentiate

A

as they migrate outwards to the surface, where they are shed

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8
Q

what do keratinocytes synthesis in the basal layer

A

variety of keratin filaments and desmosomal proteins (make up the cytoskeleton)

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9
Q

what do keratinocytes become in the granular layer

A

lipid and lipid hydrolyses

- from a water tight intercellular lipid bilayer

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10
Q

what do the lamellar bodies produce

A

abundant quantities of pro-fillagrin which is covered to fillagrin in the outer layer of cells or stratum corneum

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11
Q

what are the 2 roles of filaggrin

A
  • holding moisture within the cells

- component of tough protein cell envelope

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12
Q

what happens to cells as they migrate outwards

A

they die, lose their nuclei and flatten into squames

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13
Q

what is the outer stratum corneum like

A

tissue-paper thin but provides most fo the barrier function of the epidermis

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14
Q

what does filaggrin deficiency lead to

A

leaky skin that loses water and allows entry of allergens that trigger an immunological response

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15
Q

what does loss of function mutation of filaggrin cause

A

dry, scaly skin complaint, ichthyisus vulgarisms

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16
Q

how long does it take for keratinocytes to migrate for the basal layer to the skin surface

A

30 days

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17
Q

how long does it take for keratinocytes to migrate from basal layer to the skin surface in psoriasis

A

quicker than 30 days

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18
Q

what do keratinocytes secrete

A
  • cytokines (interleukins)
  • interferon-gamma
  • TNF
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19
Q

what are the cells in the epidermis

A
  • keratinocytes
  • melanocytes
  • Merkel cell s
  • langerhans cells
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20
Q

where do melanocytes originate from

A

neural crew

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21
Q

where do melanocytes reside

A

in the basal layer

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22
Q

what’s more abundant keratinocytes or melanocytes

A

keratinocytes

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23
Q

what do melanocytes synthesise

A

pigment melanin

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24
Q

where is melanin transferred into

A

surrounding keratinocytes to give protection against UV radiation

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25
Q

what are racial differences in skin colour due to

A

variation in melanin production (not melanocytes number)

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26
Q

where are Merkel cells found

A

in the basal layer

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27
Q

where are Merkel cells numerous

A

on fingertips and in the oral cavity

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28
Q

what do Merkel cells play a role in

A

sensation

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29
Q

what are langerhans cells

A

dendritic cells

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30
Q

where are langerhans cells derived

A

in the bone marrow

31
Q

what do langerhans cells form

A

a network across the supra-basal layer

32
Q

what do langerhans cells playa a role in

A

antigen presenting and in immunoregulation

33
Q

how is the epidermis anchored to the dermis

A

by a complex meshwork of proteins that link the keratin intermediate filaments of basal keratinocytes to collagen fibres in the superficial dermis

34
Q

what is the joining part called

A

basement membrane zone

35
Q

what can an. autoimmune deficiency of the connecting proteins cause

A

skin fragility and a variety of blistering diseases

36
Q

what is the dermis origin

A

mesodermal origin

37
Q

what is the dermis

A

matriculates of collagen and elastin fibres, surrounded by an extracellular gel-like substance

38
Q

what do the dermis fibres give skin

A

its strength and elasticity

39
Q

what cells does the dermis contain

A
  • fibroblasts
  • mast cells
  • lymphocytes
  • dermal dendritic cells
40
Q

what does the dermis contain

A
  • blood
  • lymphatic vessels
  • nerves
  • muscle
  • appendages (sweat glands, sebaceous glands and hair follicles)
41
Q

what is the lower reticular dermis like

A

thicker and denser

42
Q

where are eccrine sweat glands found

A

throughout the skin

43
Q

what are eccrine sweat glands responsible for

A

thermoregulation sweating

44
Q

where are apocrine sweat glands found

A

in the axillae and anogenital area

45
Q

when do apocrine sweat glands function

A

not until puberty

46
Q

when are sebaceous glands active

A

after puberty

47
Q

what do sebaceous glands secrete

A

oily substance called sebum

48
Q

how does sebum pass on to the skin surface

A

via the pilosebaceous duct (hair follicle)

49
Q

where are sebaceous glands found mostly

A

on the face, scalp and upper torso

50
Q

what fibres transmit touch, pain and itch

A

sensory nerve fibres

51
Q

what does the dermal autonomic innervate

A
  • sweat glands
  • blood vessels
  • arrectores pilorum muscles
  • controls skin thermoregulatory function
52
Q

what is the skin surface covered in

A

hair

53
Q

how does hair arise

A

from modified downgrowth of epidermal keratinocytes into the dermis

54
Q

what does the hair shaft contain

A
  • inner and outer root sheath
  • cortex
  • medulla
55
Q

what does the lower part of the hair follicle contain

A

expanded bulb (contains melanocytes)

56
Q

how does the hair regrow after shedding

A

from the bulb

57
Q

what are the growth cycle of hair follicles

A
  • anagen (growth)
  • catagen (involution)
  • telogen (shedding)
58
Q

what stage of the cycle is most hair at

A

anagen

59
Q

what is grey hair due to

A

decreased tyrosine activity in the hair bulb melanocytes

60
Q

what is white hair due to

A

total loss of the melanocytes

61
Q

what are the 3 types of hair

A
  • terminal
  • vellus
  • lanugo
62
Q

what is terminal hair

A

medullated coarse hair e.g. scalp, beard, pubic

63
Q

what is vellus hair

A

non-medullated fine, downy hairs seen on the face of women and in pre-pubertal children

64
Q

what is lanugo hair

A

non-medulalted fetal hair seen in permature babies and occasionally in malnourished people

65
Q

what are nails

A

tough plates of hardened keratin

66
Q

where do nails arise

A

in nail matrix

67
Q

how long does it take to grow a fingernail

A

6 months

68
Q

how long to grow a toenail

A

1 year

69
Q

what does the subcutaneous layer consist of

A

adipose tissue

70
Q

how is subcutaneous layer arranged into

A

lobules

71
Q

how is the subcutaneous layer separated

A

by fibrous septa

72
Q

what does the subcutaneous layer contain

A

blood vessels and nerves

73
Q

what does the subcutaneous layer provide

A

insulation and cushioning against trauma

dermatology (3 decks)

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