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Dermatology > Structure and Function > Flashcards

Structure and Function Flashcards

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1
Q

is skin the largest vital organ in the body

A

yes

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2
Q

what is the epidermis

A

outer layer of the skin

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3
Q

what type of cells make the epidermis

A

stratified cellular epithelium

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4
Q

where is the dermis

A

beneath the epidermis

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5
Q

what makes the dermis

A

connective tissue

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6
Q

what embryological layer makes the epidermis

A

ectoderm- forms a single layer periderm which then casts off

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7
Q

what skin layer does the mesoderm make

A

dermis

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8
Q

what embryological layer makes melanocytes

A

pigment cells from neural crest

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9
Q

what is gastrulation

A

cellular organisation of embryo in days 7-10 into germ layers

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10
Q

list from outermost to innermost the layer of skin at 4 weeks

A

periderm
basal layer
dermis

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11
Q

list from outermost to innermost the layer of skin at 16 weeks

A 
keratin layer 
granular layer 
prickle cell layer
basal layer 
dermis

(same as adult skin, develops at 16)

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12
Q

describe blaschko’s lines

A

developmental growth pattern of skin- not following vessels, nerves or lymphatics

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13
Q

how can skin disease be traced back to the original diseased cell

A

by following blaschko’s lines

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14
Q

what is between the epidermis and the dermis

A

dermo-epidermal junction

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15
Q

what is the sub cutis

A

predominantly fat- gives elasticity

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16
Q

what muscle controls movement of the hair

A

arrector pilli

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17
Q

where in skin do blood vessels run

A

in dermis

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18
Q

what are the structural keratins in the epidermis called

A

keratinocytes

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19
Q

what other cells make up the epidermis (3)

A

melanocytes, langerhans cells, merkel cells

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20
Q

what are the epidermal cell layers (outer to inner)

A

keratin layer
granular layer
prickle cell layer
basal layer

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21
Q

what part of the epidermis is responsible for renewal and dividing

A

basal layer

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22
Q

what do apocrine cells produce

A

sweat

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23
Q

what are callouses

A

when mechanical trauma triggers extra skin to be put down to protect epidermis

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24
Q

what regulates epidermal turnover

A

growth factors, cell death, hormones

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25
Q

when is regulation of epidermal turnover lost (goes too fast)

A

skin cancer psoriasis

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26
Q

when can regulation of epidermal turnover vary

A

with age, time of year (faster in summer), stress, genetics

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27
Q

what is the white stuff is psoriasis

A

thickened keratin that doesn’t come off

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28
Q

why is psoriasis red

A

as broadened prickle layer- varies between thick and thin, shows blood vessels beneath

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29
Q

where do keratinocytes migrate from

A

basement membrane

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30
Q

describe the basal layer

A

usually one cell thick, small cuboidal cells, lots of intermediate filaments (keratin), highly metabolically active (stem cells)

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31
Q

where is the basal layer

A

between the dermis and epidermis

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32
Q

why is it called the prickle layer

A

as daughter cells move upward from the basal membrane erratically and don’t permanently stick to each other

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33
Q

what are desmosomes

A

connections between cells in the prickle layer

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34
Q

what types of cells are in the prickle layer

A

larger polyhedral cells

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35
Q

what connects to desmosomes

A

intermediate keratin filaments

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36
Q

what creates the granular layer

A

when prickle cells surface they produce proteins (filaggrin and keratin) which make large keratohyalin granules. the cell then dies and granules are released creating a cornified envelope, sealing the skin (nucleus of cell lost)

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37
Q

how does the keratin layer help moisturise the skin

A

as proteins broken down into amino acid which bind to water

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38
Q

what cells make up the keratin layer

A

corneocytes- overlapping non- nucleated cell remnants

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39
Q

what are warts caused by and how

A

human papiloma virus infects keratinocytes, triggers body to have higher level of proliferation to get rid of virally infected cell= making warts

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40
Q

where are the mucosal membranes

A

eyes, mouth, nose, genito-urinary and GI tracts

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41
Q

why are the masticatory parts of the oral mucosa keratinised

A

to deal with friction and pressure

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42
Q

is the lining of the oral mucosa keratisied

A

no

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43
Q

why do mucosal surfaces become white

A

as mucosa has become thickened and can no longer see blood vessels

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44
Q

what cell type lines blood vessels

A

endothelium- simple squamous

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45
Q

describe the epithelia on the palm of the hand

A

thick keratin layer, undulation follow those of underlying dermis giving ridges of fingerprints

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46
Q

describe the epithelia of the sole of the foot

A

very thick keratin layer, helical structures in kerating layer are terminal parts of sweat ducts

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47
Q

describe eccrine sweat glands and list where they are found

A

found over the whole body except the lips and genitals.

coiled tubular structures which regulate hear and salt loss

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48
Q

where are sebaceous glands not present

A

in palm and sole of feet

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49
Q

where are the apocrine sweat glands

A

axillae, nipples, genitals

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50
Q

what provides the tensile and elastic quality of skin

A

collagen fibres and elastic fibres

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51
Q

what ‘senses’ tactile sensation

A

meissner’s corpuscles

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52
Q

what ‘senses’ deep pressure

A

pacinian corpuscles

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53
Q

where are free nerve endings located in the skin and what do they sense

A

located in the basal layer of the epidermis, sense pain

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54
Q

where are the meissner’s corpuscles located

A

in the dermis, just beneath the epidermis- abundant in tactile areas (fingers and toes)

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55
Q

where are pacinican corpuscles located

A

deep dermis- frequently in fingerpulp

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56
Q

describe the contents of a hair follicle

A

central medulla containing ‘soft’ keratin

outer cortex of ‘hard’ keratin

papilla (bulge at base)

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57
Q

what does the papilla of the hair molecule contain

A

multiple vascular channels, the hair matrix and dermal papilla

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58
Q

what does the matrix region of the hair follicle contain

A

keratin producing cells

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59
Q

what are nails and the four layers making them

A

plates of cells filled with hard keratin

nail plate- sits in nail bed
matrix- cells divide and then produce hard keratin
cuticle- extension of the skin fold covering the nail root
hyponychium- secures the nails free edge

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60
Q

what is seen histologically in acute dermatitis

A

intra-epidermal vesicles (containing white cells, fluid and cell debris)

spongiosis- intracellular oedema

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61
Q

what is seen histologically in psoriasis

A

parakeratosis in keratin layer

micro abscesses in epidermis

elongated rete pegs (downward projections of the epidermis into the dermis)

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62
Q

why does a bioposy of the sole of the foot have a prominent granular layer

A

as needed to maintain thick keratin layer

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63
Q

what is bullous pemphigoid

A

formation of blisters

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64
Q

what inflammatory cell is seen in bullous pemphigoid stained red

A

eosinophils (inside the fluid filled bulla) between the epidermis and dermis)

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65
Q

what forms a blisters roof

A

the epidermis

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66
Q

black dots on histological slides are what

A

lymphocytes= inflammation

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67
Q

what is parakeratosis

A

where cells retain their nuclei

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68
Q

what are the main functions of the skin (6)

A

barrier against water loss and entry of unwanted substances

metabolism and detoxification

immune defence

sociosexual

sensory function

thermoregulation

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69
Q

what induces toxic epidermal necrolysis (TEN)

A

drugs

70
Q

what is toxic epidermal necrolysis

A

keratinocyte death resulting in epidermal detachment at the dermoepidermal junction (skin detaches in large necrotic sheets

71
Q

what are the components of skin failure

A

loss of thermoregulation (may contribute to cardiovascular instability)

increased risk of infection

failure of homeostatic function (fluid and electrolyte losses, cardiovascular instability)

72
Q

what is needed for healthy skin (6)

A

intact physical barrier (hydration, infections)

functioning immune system

functioning vasculature (oxygenation, venous and lymphatic drainage, temperature regulation)

sensory nerve function (injury)

sweat glands (thermoregulation)

nutrition

73
Q

what is a wound

A

any break in the skin

74
Q

what cell types are present in acute wound resolution in the three main layers of skin

A

epidermis- keratinocytes

dermis-fibroblasts

sub-cutaneous fat- macrophages

75
Q

what are the three stages of healing

A

inflammation, proliferation and tissue remodelling

76
Q

what is the role of platelets in healing

A

form the initial clot and release inflammatory mediators

77
Q

what is the role of leucocytes in healing

A

debride the wound bed by phagocytosing bacteria and scavenging cellular debris

78
Q

what is the role of fibroblasts in healing

A

lay down matrix and contract the wound (fibroplasia). then lay down collagen to improve the tensile strength of the scar and restore the normal dermal matrix

79
Q

what is angiogenesis

A

when endothelial cells develop into new blood vessels

80
Q

what is the differnce between primary and secondary intention

A

primary- an acute wound is closed is closed by approximating wound edges (eg suture)

secondary- an acute wound is left to heal on its own

81
Q

describe the degrees of burns

A

first- epidermis only

second/partial thickness- epidermis and dermis

third/ full thickness- extends beyond dermis

82
Q

when is a wound considered chronic

A

if it doesnt heal within three months

83
Q

what is a surface slough

A

seen in chronic wounds- a mixture of dead cells, polymorphs and bacteria

it is yellow/ green and may stick to underlying tissue

should be removed as has inhibitory effects on healing

84
Q

what can cause delayed healing

A

infection, poor arterial supply, poor nutrition, impaired venous return, repeated trauma/ pressure, systemic disease (diabetes, anaemia)

85
Q

what leads to a diabetic foot ulcer

A

neuropathy and microvascular disease

86
Q

what leads to a venous leg ulcer

A

leaky valves create high back pressure in leg veins (varicose) creating stasis and unhealthy skin which breaks down easily

87
Q

what causes a bed sore

A

prolonged pressure over bony area + lack of blood flow (2-3 hours), + friction from bedding/ clothing + sweat, blood, urine or faeces = erosion and ulceration of the skin

88
Q

what is a scar

A

a loss of appendages

89
Q

what is a kerantinocyte

A

an epidermal cell which produces keratin

90
Q

what are the types of epidermal cell

A

keratinocytes (95%), melanocytesm langerhans, merkel cells

91
Q

where do melanocytes migrate from

A

neural crest to the epidermis (in first 3 months of foetal development)

92
Q

where are melanocytes found

A

basal layer and above

93
Q

what are melanocytes

A

pigment producing dendrititic cells

94
Q

how do melanocytes produce produce pigment

A

organelles called melanosomes convert tyrosine to melanin pigment

95
Q

what pigment creates brown and black pigment

and red and yellow

A

B+B eumelanin

R+Y phaeomelanin

96
Q

what is the role of melanin

A

absorbs light, forms protective caps to protect the nuclear DNA in basal cells

97
Q

what transforms full melanosomes (melanin granules’ to adjacent keratinocyte (which absorbs them)

A

dendrites

98
Q

what stimulates the formation of melanin

A

UV radiation and hormones

99
Q

what is vitiligo

A

an autoimmune disease with loss of melanocytes (attacked by T cells) leading to patches lacking in pigment

100
Q

why dont you want to treat a patient with vitiligo with melanotan

A

may transform into malignant melanoma

101
Q

what causes albinism

A

genetic disorder with partial pigment production in melanocytes

102
Q

what is nelson’s syndrome

A

tumour producing too much ACTH which stimulates the pituitary gland to produce melanin stimulating hormone in excess leading to hyperpigmentation

103
Q

where do langerhan cells come from

A

mesenchymal origin- bone marroe

104
Q

where are langerhans cells in the skin

A

prickle cell level in the epidermis

105
Q

where else other than skin are langerhans found

A

dermis and lymph nodes

106
Q

what is the role of langerhan cells

A

involved in skin immune system:

  • antigen presenting cells
  • pick up antigen in skin and circulate to lymph nodes via lymphatic system
107
Q

what is the racket shaped organelle in langerhan cells

A

birbeck granules

108
Q

where are merkel cells

A

basal, between keratinocytes and nerve fibres

109
Q

what are merkel cells

A

mechanoreceptors

110
Q

what causes merkle cell cancer caused by

A

viral infection, rare with high mortality

111
Q

what is a pilosebaceous unit

A

a hair follicle

112
Q

what creates hair pigmentation

A

melanocyes above dermal papilla

113
Q

what layer of skin does hair grow out of

A

basal layer

114
Q

describe the structure of hair

A

medulla, internal root sheath, cortex, external root sheath

115
Q

what is acne and its mechanism

A

bacteria living in pilo-sebaceous units, eating the complex sugar and breaking it down into small fatty acids which is oxidised on the skin and acts as a pro inflammatory

116
Q

what do retinoids do

A

block the formation of sebum- drying the skin starving the bateria of food

117
Q

what are the three phases of hair growth

A

anagen- growing
catagen- involuting
telogen- resting

118
Q

name 2 hormones that can influence hair growth

A

thyroxine and androgens

119
Q

what are the three types of hair follicle

A

lanugo (in utero), vellus, terminal

120
Q

how much hair is shed a day

A

50-100

121
Q

what is at the base of a hair follicle

A

the papilla which is surrounded by the matrix

122
Q

can pregnancy affect hair growth

A

yes

123
Q

what is virilisation

A

growth of facial hair on females do to excess androgen form a tumour

124
Q

what is alopecia areara

A

autoimmune hair loss- usually reversible and grows back

125
Q

what cell type are nails

A

specialised keratins

126
Q

where do nails grow from

A

nail matrix/ root (similar to hair bulb)

127
Q

what is the dermo-epidermal junction

A

interface between epidermis and dermis

128
Q

what is the role of the DEJ

A

epithelial- mesenchymal interaction;
support, anchorage, adhesion, growth and differentiation of basal cells

semi permeable membrane acting as a barrier and filter

129
Q

what are the layer (3) of the dermo epidermal junction

A

lamina lucida
lamina densa
sub-lamina densa zone

130
Q

name two conditions caused by defects in the DEJ

A
  • bullous pemphigoid

- epidermolysis bullosa

131
Q

what cells are found in the dermis

A

fibroblasts, macrophages, mast cells, lymphocytes, langerhans cells

132
Q

what fibres are found in the dermis

A

collagen (gives strength)

elastin (gives elasticity)

133
Q

what do fibroblasts do

A

synthesises extracellular matrix and collagen

134
Q

why is the blood vessel supply in the dermis greater than metabolic needs

A

to thermoregulate

135
Q

how do blood vessels travel in the dermis

A

horizontal plexuses

136
Q

what is the path of vasculature from arteriole to collecting venules

A

precapillary sphincters- arterial- venous capillaries- post capillary venules- collecting venules

137
Q

what is angioma

A

overgrowth of blood vessels (benign)

138
Q

what is dermographism

A

exaggerated wealing tendency when the skin is stroked

139
Q

how do the lymphatic vessels travel in the skin

A

sub epidermal meshed networks (horizontal plexus same as vasculature)

140
Q

what do lymphatic vessels continually drain

A

plasma proteins, extravasated cells, excess interstitial fluid

141
Q

what are the immune functions of lymph vessels

A

immune surveillance by circulating lymphocytes and langerhans cells

channelling of microorganisms/ toxins

142
Q

what is chronic lymphoedema

A

localised fluid retention and swelling due to a compromised lymph system

143
Q

what is the most common infection in lymphoedema

A

cellulitis

144
Q

what are dermatomes responsible for

A

somatic sensory (free nerve endings and special receptors)

145
Q

what do free nerve endings do

A

open directly onto skin surface for pain and temp

146
Q

what is neurofibromatosis

A

overgrowth of nerve endings

147
Q

what are sebaceous gland and what is their role

A

holocrine secretion opening into pilary canal

produce sebum to control moisture loss and protect from fungal infection

148
Q

what is the mechanism behind cystic acne

A

too much oil, oxidised on the ski surface blocking and inflaming pore

149
Q

what and where are apocrine glands

A

only active when you hit puberty (androgen dependent), in the axiallae and perineum, produce oily fluid that has an odour after bacterial decomposition

150
Q

where are eccrine sweat gland

A

whole skin surface (especially palms, soles and axillae)

151
Q

what nerve supplies eccrine sweat glands

A

sympathetic cholingeric nerve supply

152
Q

what stimulates eccrine sweat glands

A

mental, thermal and gustatory (food) stimulation

153
Q

what is hyperhydrosis

A

excessive sweat production

154
Q

what causes toxic epidermal nercolysis

A

drugs

155
Q

what is acute skin failure

A

when over 90% of skin fails

156
Q

why may you become hypoalbumaenic in TEN

A

as losing water, albumin in water also lost

157
Q

what is erythroderma

A

intense and widespread reddening of the skin

158
Q

what metabolic consequences arise from acute skin failure

A

disordered thyroxine metabolism

159
Q

what causes steroid-sulphatase deficiency x-linked ichthyosis

A

deficiency in normal lipids in keratin layer

160
Q

what is the ratio between melanocytes and keratinocytes

A

1:10

161
Q

what is the skin role is metabolism

A

vit d metabolism and thyroid hormone metabolism

162
Q

describe the metabolism of vitamin D

A

Vit d3 stored as hydroxycholecalciferol in liver then converted to 1,25-dihydroxycholecaliferol in kidney

163
Q

why is vit d important

A

for calcium absorption, deficiency causes rickets

164
Q

where does the conversion of thyroxine in thyroid hormone metabolism occur

A

20% in thyroid gland

80% in peripheral (to thyroid) tissues including skin

165
Q

what is crusted scabies

A

a severe form a scabies which occurs in a person with a compromised immune system

166
Q

what is hansens disease

A

tuberculoid leprosy

167
Q

what is the mechanism of leprosy

A

intracellular mycobacteria act on the Schwann cells producing a chronic granulomatous reaction resulting in the destruction of both myelin and the underlying nerve cells.The damage to nerves and their protective outer layers leads to permanent neurological damage.

168
Q

what is eczema herpeticum

A

disseminated herpes simplex virus infection in people with ectopic eczema tendency

169
Q

define stigma

A

the situation of an individual who is disqualified from full social acceptance

170
Q

what is dermatitis herpaformis

A

chronic blistering condition, autoimmune condition linked to coeliac disease

171
Q

what is a neuropathic ulcer

A

skin sore cuased by lack of feeling (neuropathy commonly from diabetes mellitus or less commonly leprosy

Dermatology (23 decks)

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