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Dermatology SB > Structure and Function of Skin > Flashcards

Structure and Function of Skin Flashcards

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1
Q

what are the layers of skin and type of cells do they consist of

A

1) epidermis - outer layer
- stratified cellular epithelium

2) dermis - beneath epidermis
- connective tissue

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2
Q

how does the epidermis form (embryology)

A

ectoderm cells form single layer periderm
gradual increase in layers of cells
periderm cells cast of

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3
Q

where does dermis come from (embryology)

A

formed from mesoderm below ectoderm

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4
Q

what are melanocytes and where do they migrate to

A

pigment producing dendritic cells

neural crest

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5
Q

what happens around 7-10 days in early foetal development

A

gastrulation

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6
Q

what layers are there after 4 weeks development

A

Periderm
Basal layer
Dermis (corium)

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7
Q

what layers are there at 16 weeks development

A 
Keratin layer
Granular layer
Prickle cell layer
Basal layer
Dermis
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8
Q

what are Blaschko’s lines

A

developmental growth pattern of skin

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9
Q

true or false - blaschko’s lines follow vessels

A

false

they do not

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10
Q

what separates the epidermis from the dermis

A

the dermo-epidermal junction

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11
Q

what are the cells of epidermis

A

keratinocytes (95%)
melanocytes
langerhans cells
merkel cells

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12
Q

what are the layers of the epidermis - top to bottom

A

keratin layer
granular layer
prickle cell layer
basal layer

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13
Q

what causes the hair on you arms to stand up

A

arrector pilli muscle

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14
Q

what regulates epidermal turnover

A

growth factor
cell death
hormones

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15
Q

what are diseases where the epidermal turnover is affected

A

skin cancer

psoriasis

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16
Q

where do keratinocytes migrate from and how long does it take

A

basement membrane

takes 28 days from bottom to top

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17
Q

description of basal layer

A

Usually one cell thick
Small cuboidal
Lots of intermediate filaments (keratin)
Highly metabolically active

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18
Q

description of prickle cell layer

A

Larger polyhedral cells
Lots of desmosomes (connections)
Intermediate filaments connect to desmosomes

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19
Q

description of granular layer

A

2-3 layers of flatter cells
Large keratohyalin granules – contain structural filaggrin & involucrin proteins
High lipid content
cell nuclei lost

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20
Q

what originates in the granular layer

A

the cornified envelope

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21
Q

what does the granular layer contain

A

odland bodies (lamellar bodies)

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22
Q

what is contained in the keratin layer

A

corneocytes - overlapping non-nucleated cell remnants

lamellar granules - release lipid

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23
Q

where does the cornified envelope become insoluble

A

keratin layer

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24
Q

what are the features of oral mucosa

A

Masticatory – keratinised to deal with friction/pressure
Lining mucosa – non-keratinised
Specialised mucosa - tongue papillae (for taste)

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25
Q

where are melanocytes found

A

in basal layer and above

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26
Q

what do melanocytes contain and how and where are they transferred

A

melanosomes

transferred to adjacent keratinocyte via dendrites

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27
Q

what is melanocytes function

A

convert tyrosine to melanin pigment (eumelanin and phaeomelanin)

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28
Q

what does melanin do

A

absorbs light

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29
Q

true or false - melanosomes form a protective cap over nucleus

A

true

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30
Q

what is nelson’s syndrome

A

melanin stimulating hormone is produced in excess by the pituitary

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31
Q

where do langerhans cells originate and where are they found

A

bone marrow
prickle cell layer and above
also in dermis and lymph nodes

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32
Q

what is the function of langerhans cells

A

involved in skin immune system
antigen presenting cells
Pick up antigen in skin and circulate to lymph nodes via lymphatic system

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33
Q

where are merkel cells found and what do they do

A

basal layer between keratinocytes & nerve fibres

mechanoreceptors

34
Q

what is pilosebaceous unit

A

hair follicles

35
Q

what does hair follicles consist of

A

Epidermal component plus dermal papilla

Adjacent sebaceous gland

36
Q

what does hair follicles contain

A

specialised keratins

37
Q

what are the phases of growth of hair follicles

A

anagen - growing
catagen - involuting
telogen - resting

38
Q

what is the most common cause of human hair-loss

A

telogen effluvium

39
Q

what is virilisation and what causes it

A

male features developing in women

excess androgen

40
Q

what is an autoimmune cause of hair loss

A

alopecia areata

41
Q

what are nails made of and what is the growth rate

A

specialised keratins

0.1mm per day (fingers>toes, summer>winter)

42
Q

what is the role of the demo-epidermal junction

A

support, anchorage, adhesion, growth and differentiation of epidermal cells
semi-permeable membrane acting as barrier and filter

43
Q

inherited diseases of DEJ

A

epidermolysis bullosa: simple (EBS) or dystrophic (EBD)

44
Q

causes of congenital disease of DEJ and examples

A

auto-antiobides to proteins in DEJ

e.g. pemphigus, pemphigold, dermatitis herpetiformis

45
Q

what are the components of the dermis

A

cells - fibroblasts, macrophages, mast cells, lymphocytes,

Langerhans cells

fibres - collagen (majority) and elastin

46
Q

what are the function of fibroblasts

A

make collagen and elastin

47
Q

true or false - skin has a small blood supply

A

false

supply is greater than metabolic need

48
Q

what is the flow of blood in the skin

A

Arteriole — precapillary sphincters — arterial capillaries —venous capillaries – post-capillary venules — collecting venules

49
Q

what is an angioma

A

localised overgrowth of blood vessels

e.g. port wine stain, “stork marks:

50
Q

what is the function of lymphatic vessels

A
  • immune surveillance by circulating lymphocytes and Langerhans cells
  • channelling of micro-organisms / toxins
  • Continual drainage of plasma proteins, extravasated cells and excess interstitial fluid
51
Q

what does the loss of protein in the skin lead to

A

oedema

52
Q

what nerves are responsible for sensing pressure on skin

A

pacinain corpuscles

53
Q

what nerves are responsible for sensing vibration on skin

A

meissners corpuscles

54
Q

what are the types of nerves in the skin - top to bottom

A 
free nerve ending 
meissners corpuscles
sensory nerve fibre
pacinian corpuscle 
motor nerve fibre
55
Q

what are neurofibromatosis

A

overgrowth of the nerve endings

56
Q

what are the 3 type of skin glands

A

Sebaceous
Eccrine
Apocrine

57
Q

description of sebaceous glands

A

Widely distributed:
- largest glands present on face and chest
Hormone sensitive – inactive pre-puberty

58
Q

what does sebaceous glands produce and where do they mainly open up onto

A

sebum

hair follicles

59
Q

what is the function of sebaceous glands

A

control moisture loss

protection from bacterial and fungal infection

60
Q

what are sebaceous glands are part of

A

pilosebaceous unit

61
Q

what is acne a combo of

A

increased sebum, blocked ducts

and bacterial activity

62
Q

what is the function of apocrine sweat glands

A

Produce oily fluid - produce odour

Scent glands

63
Q

what do apocrine glands develop as part of

A

pilosebaceous unit

64
Q

where are apocrine glands found

A

axillae and perineum

65
Q

what are apocrine dependant on and when are they most prominent

A

androgen

after puberty

66
Q

where are eccrine glands found

A

Whole skin surface
 - palms, soles and axillae in particular

67
Q

what is the nerve supply for eccrine glands

A

sympathetic cholinergic nerve supply

68
Q

what are the functions of the eccrine glands

A

cooling by evaporation

moistens palms/soles to aid grip

69
Q

what are the functions of skin

A 
Barrier function 
Metabolism & detoxification
Thermoregulation
Immune defence
Communication
Sensory functions
70
Q

what is toxic epidermal necrolysis

A

acute skin failure

sheering off of the epidermis all over the skin

71
Q

what are the consequences of failure of barrier

A

1 - fluid loss therefore, dehydration
2 - protein loss therefore, hypoalbuminaemia
3 - infection

72
Q

what are the consequences of failure of thermoregulation

A

heat loss - hypothermia

73
Q

what are the consequences of failure of immune defence

A

spread of infection

74
Q

what are the consequences of failure of metabolic

A

disordered thyroxine metabolism

75
Q

what are the consequences of failure of sensation

A

pain

76
Q

what are the four stratum layers of epidermis - top to bottom

A

1 - stratum corneum
2 - stratum granulosum
3 - stratum spinosum
4 - stratum basale

77
Q

why does melanin cover the nuclei

A

to absorb UV rays and protect DNA in the cells nuclei

78
Q

what is vitamin D3 stores as and where

A

hydroxycholecalciferol in liver

79
Q

what happens to hydroxycholecalciferol

A

Converted to 1,25-dihydroxycholecaliferol in kidney

80
Q

what are the functions of melanosomes

A

synthesis, storage and transport of melanin

Dermatology SB (11 decks)

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