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Y2 Dermatology > Structure and Function of the Skin > Flashcards

Structure and Function of the Skin Flashcards

1
Q

what is the most common cell type in the epidermis?

A

keratinocytes

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2
Q

name three cells, that aren’t keratinocytes, that are found in the epidermis?

A

melanocytes
langerhans cells
merkel cells

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3
Q

how do melanocytes reach the epidermis?

A

they migrate from the neural crest in the first 3 months of foetal development

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4
Q

where are melanocytes found?

A

in and above the basal layer

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5
Q

what are melanocytes?

A

pigment producing dendritic cells

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6
Q

what are the organelles found in melanocytes called?

A

melanosomes

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7
Q

how do melanocytes produce melanin?

A

they convert tyrosine to melanin pigment

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8
Q

what are the two types of melanin?

A

eumelanin

pheomelanin

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9
Q

what colour is eumelanin?

A

brown or black

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10
Q

what colour is phaeomelanin?

A

red or yellow

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11
Q

what does melanin absorb?

A

light

it acts as a neutral density filter

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12
Q

where and how are full melanosomes transferred?

A

to adjacent keratinocytes

via dendrites

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13
Q

what do melanosomes form?

A

a protective cap over the cell nucleus, to protect the DNA in basal cells

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14
Q

what is vitiligo?

A

an autoimmune disease where melanocytes are lost

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15
Q

what is involved in albinism?

A

a genetic partial loss of pigment production

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16
Q

what occurs in nelson’s syndrome?

A

melanin stimulating hormone is produced in excess by the pituitary

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17
Q

what is a malignant melanoma?

A

a tumour of melanocytes

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18
Q

where do langerhans cells originate?

A

bone marrow (mesenchymal)

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19
Q

where are langerhans cells found?

A

the prickle cell layer of the epidermis

the dermis

lymph nodes

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20
Q

what type of cells are langerhans cells?

A

antigen presenting cells

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21
Q

where are merkel cells located?

A

basal layer

between keratinocytes and nerve fibres

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22
Q

what type of cells are merkel cells?

A

mechanoreceptors

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23
Q

what causes merkel cell cancer?

A

a viral infection

this is very rare and has a high mortality rate

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24
Q

what causes hair pigmentation?

A

melanocytes above the dermal papilla

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25
Q

what forms a pilosebaceous unit?

A

epidermal component
dermal papilla
specialised keratins
adjacent sebaceous gland

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26
Q

what does a sebaceous gland produce?

A

sebum

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27
Q

what is sebum?

A

a greasy wax that acts as a natural emollient

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28
Q

where is hair always found?

A

with a sebaceous gland

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29
Q

what are the three phases of hair growth?

A

anagen
catagen
telogen

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30
Q

which phase of hair growth is the growing phase?

A

anagen

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31
Q

which phase of hair growth is the resting phase?

A

telogen

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32
Q

which phase of hair growth is the involuting phase?

A

catagen

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33
Q

name two hormonal influences on hair growth?

A

thyroxine

androgens

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34
Q

name three types of hair

A

lanugo
vellus
terminal

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35
Q

where is lanugo hair found?

A

in utero

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36
Q

which phase of hair growth is asynchronous in humans?

A

telogen

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37
Q

what is alopecia areata?

A

autoimmune hair loss

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38
Q

what are nails made from?

A

specialised keratins

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39
Q

what is the growth rate for nails?

A

0.1mm per day

occurs more on the fingers and in summer

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40
Q

what is the largest vital organ in the body?

A

the skin

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41
Q

what can skin disease indicate?

A

underlying disease

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42
Q

what are the two layers of the skin?

A

epidermis

dermis

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43
Q

what is the outer layer of the skin?

A

epidermis

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44
Q

what is the epidermis?

A

a very thin layer of stratified squamous epithelium

45
Q

what is the epidermis made of?

A

connective tissue

46
Q

what is the role of the dermis?

A

provides mechanical strength

47
Q

how does the epidermis develop in an embryo?

A

ectoderm cells form a single layer periderm, which builds up and is eventually cast off, forming the epidermis

48
Q

what forms the dermis in an embryo?

A

cells from the mesoderm

49
Q

what are melanocytes?

A

pigment producing dendritic cells

50
Q

where do melanocytes originate in development?

A

the neural crest

51
Q

what are the development growth lines of skin called?

A

blaschko’s lines

52
Q

what is the sub-cutis predominantly made from?

A

fat

53
Q

what is another name for the sub-cutis?

A

subcutaneous tissue

54
Q

what is the main cell type in the epidermis, and what do these cells contain?

A

keratinocytes

contain structural jeratins

55
Q

how does skin grow?

A

from the basement layer to the top

56
Q

what are the four defined layers of the epidermis from bottom to top?

A

basal layer
prickle cell layer
granular layer
keratin layer

57
Q

name four cell types found in the epidermis?

A

keratinocytes
melanocytes
langerhans cells
merkel cells

58
Q

what type of cells are found in the basal layer?

A

stem cells

59
Q

what layer of the epidermis is very thick on the palms and the soles?

A

the keratin layer

60
Q

how thick is the granular layer of the skin of the hands and feet normally?

A

around one cell thick

61
Q

what three things control epidermal turnover?

A

growth factors
cell death
hormones

62
Q

name two conditions that can be caused by loss of regulation of epidermal turnover

A

skin cancer

psoriasis

63
Q

what is the majority of the dermis made from?

A

collagen fibres

64
Q

what cell type produces collagen fibres?

A

fibroblasts

65
Q

how long does it take the skin to regenerate from bottom to top?

A

28 days

66
Q

how thick is the basal layer normally?

A

one cell thick

67
Q

what are the cells of the basal layer like?

A

small and cuboidal

68
Q

what is there lots of in the basal layer?

A

intermediate filaments such as keratin

69
Q

which layer of the epidermis is very metabolically active?

A

the basal layer

70
Q

describe the cells of the prickle cell layer

A

large

polyhedral

71
Q

what cell feature is found in the prickle cell layer?

A

lots of desmosomes with intermediate filaments attached

72
Q

describe a normal granular layer

A

two to three layers of flat cells

73
Q

name two things found in the granular layer

A

keratohyalin granules

odland bodies

74
Q

what do keratohyalin granules contain?

A

structural proteins i.e. filaggrin and involucrin

75
Q

describe the masticatory oral mucosa

A

keratinised

this is to deal with friction

76
Q

describe the lining mucosa of the oral cavity

A

non keratinised

77
Q

what does the mucosa of the tongue contain?

A

papillae

78
Q

what does the ocular mucosa contain?

A

lacrimal glands
eyelashes
sebaceous glands

79
Q

what is the dermo-epidermal junction (DEJ)?

A

the interface between the epidermis and the dermis

80
Q

how does the epidermis receive nutrients?

A

no blood supply

all nutrients diffuse up from the dermis

81
Q

where are sweat glands and hair follicles located?

A

the dermis

82
Q

what is another name for the upper dermis?

A

the papillary dermis

83
Q

what is another name for the DEJ?

A

the basement membrane

84
Q

what are the three layers of the DEJ?

A

lamina lucida
lamina densa
sub lamina densa

85
Q

name two diseases caused by problems with the DEJ

A

bullous pemphigoid

EB

86
Q

what is the dermis made of?

A

ground substance
cells
fibres

87
Q

what is ground substance?

A

a supportive water based substance

88
Q

what cells are found in the dermis?

A 
fibroblasts
macrophages 
mast cells 
langerhans cells 
lymphocytes
89
Q

what two fibres are found in the dermis?

A

collagen

elastin

90
Q

what causes photoaging?

A

UV exposure

91
Q

what is the pathological process behind photoaging?

A

loss of collagen makes skin collapse

loss of elastin means the skin cant bounce back

92
Q

what supports the vessel walls in the skin?

A

collagen

muscle fibres

93
Q

what three things make up the somatic sensory supply of the skin?

A

free nerve endings
pacinian corpuscles
meissner’s corpuscles

94
Q

what do pacinian corpuscles sense?

A

pressure

95
Q

what do meissner’s corpuscles sense?

A

vibration

96
Q

what creates the pigment of hair?

A

melanocytes

97
Q

what is acne a disease of?

A

the pilosebaceous unit

98
Q

what are the three stages of hair growth?

A

anagen
catagen
telogen

99
Q

what are the three skin glands?

A

sebaceous
appocrine
eccrine

100
Q

when do sebaceous glands become active?

A

puberty

101
Q

what do sebaceous glands secrete?

A

sebum

102
Q

where are apocrine sweat glands found?

A

axillae

perineum

103
Q

what are the main sweat glands?

A

eccrine

104
Q

what is the two way barrier of the skin?

A

epidermis

105
Q

what is steroid sulphatase deficiency?

A

an inherited disorder of steroid sulphates

lipids in the keratin layer are not formed

106
Q

what two substances are metabolised by the skin?

A

vitamin D

thyroid hormone

107
Q

what is the reaction of vitamin D metabolism in the skin?

A

UVB reactions convert 7-dehydrocholesterol to vitamin D

108
Q

what is the reaction of thyroid hormone metabolism in the skin?

A

thyroxine is converted to triiodothyronine

Y2 Dermatology (17 decks)

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