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dermatology > Physiology > Flashcards

Physiology Flashcards

1
Q

Name the 3 main layers of the skin from outside inwards

A

Epidermis
Dermis
Subcutis

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2
Q

What is the epidermis

A

Outer layer of stratified squamous epithelium

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3
Q

What is the dermis

A

Layer of connective tissue beneath the epidermis

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4
Q

What is found between the epidermis and dermis

A

Dermo-epidermal junction

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5
Q

What is the subcutis

A

The fat layer beneath the dermis

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6
Q

Where does epidermis originate from embryonically

A

Ectodermal germ layer

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7
Q

Where does the dermis originate from originally

A

Mesoderm germ layer

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8
Q

Where do melanocytes originate from

A

The neural crest

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9
Q

What happens to the skin in week 4 of development

A

Differentiation into periderm, basal layer and dermis

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10
Q

What happens to the skin in week 16 of development

A

Formation of layers: keratin, granular, prickle cell, basal
Melanocytes migrate from the neural crest

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11
Q

By what time is the skin fully formed during development

A

26 weeks

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12
Q

What are blaschko’s lines

A

Developmental growth pattern of skin thought to represent pathways of cell migration during fetal development

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13
Q

What are the 4 layers of the epidermis

A

Keratin
Granular
Prickle cell
Basal

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14
Q

What controls epidermal turnover

A

Growth factors, cell death and hormones

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15
Q

Role of the basal layer of the epidermis

A

Epidermal renewal and regeneration
Contains melanocytes for protection from UV

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16
Q

The 3 main types of cells in the basal layer of the epidermis

A

Basal cells
Keratinocytes
Melanocytes

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17
Q

What are basal cells

A

Columna or cuboidal cells that undergo rapid mitotic divisions to produce new keratinocytes

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18
Q

Structure of the basal layer of the epidermis

A

Usually one cell thick

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19
Q

Structure of the prickle cell layer of the epidermis

A

Larger polyhedral cells
Lots of desmosomes
Intermediate filaments connect to desmosomes

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20
Q

What cells are found in the prickle cell layer of the epidermis

A

Prickle cell
Keratinocytes
Langerhans cells

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21
Q

2 main function of the prickle cell layer of the epidermis

A

Structural support and immune function

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22
Q

Structure of the granular layer of the epidermis

A

2-3 layers of flatter cells

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23
Q

What cells are found in the granular layer of the epidermis

A

Keratinocytes
Keratohyalin granules
Odland bodies

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24
Q

What are odland bodies

A

Secretory organelles that contribute to skin barrier

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25
Q

What do keratohyalin granules contain

A

Filaggrin
Natural moisturising factor

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26
Q

Role of filaggrin

A

Binds to keratin intermediate filaments promoting aggregation and cross linking

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27
Q

What do odland bodies secrete

A

Keratohyalin granules

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28
Q

Role of the keratin layer of the epidermis

A

Tight waterproof barrier

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29
Q

Main cellular component of keratin layer

A

Corneocytes

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30
Q

What are corneocytes

A

Flattened non-viable cells that have undergone keratinisation, transforming them into tough and resilient structures

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31
Q

Posh name for keratin layer

A

Stratum corneum

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32
Q

Posh name for granular layer

A

Stratum granulosum

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33
Q

Posh name for prickle cell layer

A

Stratum spinosum

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34
Q

Posh name for basal layer

A

Stratum basale

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35
Q

What are melanocytes

A

Pigment producing dendritic cells

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36
Q

Role of melanosomes

A

Convert tyrosine to melanin pigment

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37
Q

What are the 2 melanin pigments

A

Eumelanin
Phaeomelanin

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38
Q

What is the role of melanin

A

Absorbs UV rays to protect DNA in the cells nuclei

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39
Q

What gene is important skin pigmentation

A

MC1R gene

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40
Q

Risk associated with mutation in MC1R gene

A

Most vulnerable to sun exposure

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41
Q

What does 1 defective copy of MC1R causes

A

Ginger hair

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42
Q

What does 2 defective copies of the MC1R gene cause

A

Ginger hair and freckles

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43
Q

Characteristics of darker skin

A

Larger melanosomes containing more melanin
More Eumelanin
Melanosomes exist through the epidermis

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44
Q

Characteristics of fairer skin

A

Smaller amounts of melanin
More phaeomelanin
Melanosomes confined to the basal layer in unexposed skin

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45
Q

Where do langerhans cells come from

A

The bone marrow

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46
Q

Role of langerhans cells

A

Antigen presenting cells

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47
Q

Where are langerhans cells found (3)

A

Prickle cell layer of the epidermis
Dermis
Lymph nodes

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48
Q

Where are merkel cells found

A

Basal layer of the epidermis

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49
Q

What is the role of a merkel cell

A

Mechanoreceptors

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50
Q

Role of masticatory oral mucosa

A

Keratinised to deal with friction and pressure

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51
Q

Role of the dermo-epidermal junction

A

Support and anchorage of basal cells
Semi-permeable membrane acting as a barrier and a filter

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52
Q

Cells found in the dermis

A

Fibroblasts
Macrophages
Mast cells
Lymphocytes
Langerhans cells

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53
Q

Role of fibroblasts in the dermis

A

Maintain ground substance
Produce collagen

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54
Q

Fibres found in the dermis

A

Collagen and elastin

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55
Q

Difference in the dermis in different skin types

A

Caucasian skin has a thinner dermis and bigger collagen fibres
AA skin has larger and more numerous fibroblasts

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56
Q

Organisation of blood vessels in the dermis

A

Horizontal plexuses

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57
Q

Name 2 special nervous receptors found in the dermis

A

Meissners corpuscle
Pacinian corpuscle

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58
Q

Where are meissners corpuscles abundantly found

A

Tactile areas of fingers and toes

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59
Q

What do meissners corpuscles detect

A

Tactile stimuli, light touch

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60
Q

What do pacinian corpuscles detect

A

Pressure

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61
Q

Where are pain receptors located in the skin

A

Basal layer of the epidermis

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62
Q

Role of collagen and elastic fibres in the dermis

A

Provide tensile strength and elastic qualities of skin

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63
Q

Name the 3 types of skin glands

A

Eccrine
Sebaceous
Apocrine

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64
Q

What do sebaceous glands produce

A

Sebum

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65
Q

What is sebum associated with

A

Acne

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66
Q

Where are sebaceous glands usually found

A

Chest, face, back

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67
Q

Functions of sebaceous gland (3)

A

Control moisture loss
Protect against fungal infection
Lubricate hair follicle

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68
Q

Sebaceous gland

A

Holocrine secretion opening into pilary canal

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69
Q

What is an apocrine gland

A

Develop as part of the philosebaceous unit

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70
Q

Where are apocrine glands found

A

Axillae, groin, eyelids, mammary and perineal regions

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71
Q

Role of apocrine glands

A

Produce oily fluid

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72
Q

What are apocrine glands dependent on

A

Androgens

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73
Q

Where are eccrine glands found

A

EVERYWHERE
particularly palms, soles, forehead and axilla

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74
Q

Role of eccrine glands (3)

A

Filtration
Cooling by evaporation
Moistens palms and soles for grip

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75
Q

What causes eccrine gland stimulation

A

Mental, thermal and gustatory stimulation

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76
Q

What is the pilosebaceous unit composed of

A

Hair follicle
Hair shaft
Arrector pili muscle
Sebaceous glands

77
Q

What are the 3 main segments of the hair follicle

A

Infundibulum
Isthmus
Hair bulb

78
Q

What does the hair bulb contain

A

Hair matrix and dermal papilla

79
Q

What does the hair matrix contain

A

Keratin producing cells

80
Q

What gives hair pigment

A

Melanocytes above the dermal papilla

81
Q

Difference in keratin between the central medulla and the outer cortex

A

Medulla contains soft keratin, and the outer cortex and cuticle contain hard keratin

82
Q

What hair type has the highest hair density

A

Caucasian hair

83
Q

What hair type has the most moisture content

A

Caucasian hair

84
Q

What type of hair has the fastest growing rate

A

Asian hair

85
Q

Which type of hair is the most fragile

A

Black hair

86
Q

Name the 3 phases of hair growth

A

Anagen, catagen, telogen

87
Q

What is the anagen phase of hair growth

A

The growing phase

88
Q

How long does the anagen phase usually last

89
Q

What proportion of hair is in the anagen phase

90
Q

What is the catagen phase of hair growth

A

Involuting phase

91
Q

How long does the catagen phase last

92
Q

What proportion of hair is in the catagen phase

93
Q

What is the telogen phase of hair growth

A

Resting phase

94
Q

What happens in the telogen phase

95
Q

What is important about the telogen phase

A

It is asynchronous

96
Q

What is the growth rate of nails

A

0.1mm per day

97
Q

Name 2 factors that influence nail growth

A

Fingers grow faster
Grows faster in summer

98
Q

Give an example of a type of drug that can increase nail growth

A

Anti-fungals

99
Q

Role of the cuticle

A

Protects from infection

100
Q

Role of the hyponychium

A

Secures the free nail edge

101
Q

What is the main role of vitamin D

A

Increase the flow of calcium into the blood stream enabling the normal mineralisation of bone

102
Q

How does vitamin D do its job

A

Promotes absorption of calcium and phosphorus from food into the intestines and reabsorption of calcium in the kidneys

103
Q

What is another name for vitamin D2

A

Calciferol

104
Q

How is vitamin D2 made

A

From inactive provitamin ergosterol in plants by the action of sunlight

105
Q

What is the most effective type of vitamin D

106
Q

Where can you find vitamin D2

A

In mushrooms

107
Q

How is vitamin D3 made

A

In the skin by the action of sunlight

108
Q

Where can you also find vitamin D3

A

Small amounts in oily fish and meat

109
Q

What is another name for vitamin D3

A

Cholecalciferol

110
Q

How is vitamin D3 stored

A

As hydroxycholecalciferol in the liver

111
Q

Where is the active, hormonal form of vitamin D found

A

In the kidneys

112
Q

Give 2 consequences of vitamin D deficiency

A

Rickets and osteomalacia

113
Q

Name the 2 places the conversion of T4-T3 can occur

A

MOSTLY in peripheral tissues including the skin
Some in the thyroid gland

114
Q

Consequences of loss of barrier function of skin

A

Fluid loss- dehydration
Protein loss- hypoalbuminaemia
Infection

115
Q

Consequences of the loss of thermoregulation function of the skin

A

Heat loss - hypothermia

116
Q

Consequence of loss of metabolic function of the skin

A

Disordered thyroxine metabolism

117
Q

What is a wound

A

Any break in the skin

118
Q

What is healing by primary intention

A

Edges are approximated by stitches leading to rapid healing

119
Q

What is healing by secondary intention

A

Sides of the wounds are not opposed so healing occurs from the bottom of the wound upwards

120
Q

When is healing by secondary intention used

A

Larger wounds that are too tight to stitch
Areas where direct closure would cause significant distortion of the surrounding tissue

121
Q

What are the 3 stages of wound healing

A

Inflammation
Proliferation
Remodelling

122
Q

What happens in the inflammation stage of wound healing

A

Platelets form initial clot and release inflammatory mediators
Leukocytes debride wound
Inflammation starts to decrease as keratinocyte proliferation and new tissue formation start

123
Q

How do leukocytes debride a wound (2)

A

Phagocytose bacteria
Scavenging cellular debris

124
Q

What happens in the proliferation stage of wound healing

A

Cells divide and re-epithelialise the wound surface
Granulation tissue formation is stimulated
Fibroplasia and angiogenesis

125
Q

What is fibroplasia

A

The formation and proliferation of fibrous tissue mostly composed of fibroblasts and collagen fibres

126
Q

What happens in the tissue remodelling phase of wound healing

A

New tissue converted into mature scar tissue
Fibroblasts lay down collagen to improve the tensile strength

127
Q

How long does a wound have to be present to be chronic

128
Q

Give an example of a chronic wound

129
Q

Common characteristic of a chronic wound

130
Q

How do chronic wounds tend to heal

A

From the edges

131
Q

What are 4 factors that contribute to pressure sores

A

Prolonged pressure over bony area
Lack of blood flow
Irritation from bodily fluids
Friction from bedding or clothing

132
Q

What is hyperkeratosis

A

Increased thickness of the keratin layer

133
Q

What is parakeratosis

A

Persistence of nuclei in the keratin layer

134
Q

What is acanthosis

A

Increased thickness of epithelium

135
Q

What is papillomatosis

A

Irregular epthelial thickening

136
Q

What is spongiosis

A

Intercellular fluid accumulation within the epidermis in the spaces between keratinocytes

137
Q

What are the 4 main classifications of inflammatory skin diseases

A

Spongiotic
Psoriaform
Lichenoid
Vesicubullous

138
Q

What characterises spongiotic skin diseases

A

Interaepidermal oedema

139
Q

What characterises psoriaform skin diseases

A

Elongation of the rete ridges

140
Q

What characterises lichenoid skin diseases

A

Basal layer damage

141
Q

What characterises vesicubullous skin diseases

A

Blistering

142
Q

Give an example of a spongiotic skin disease

143
Q

Give an example of a psoriaform skin disease

144
Q

Give an example of a lichenoid skin disease

A

Lichen planus
Lupus

145
Q

Give an example of a vescubullous skin disease

A

Pemphigus, pemphigoid
Dermatitis herpetiformis

146
Q

What is Pruritus

A

An unpleasant, poorly localised, non-adapting sensation that provokes the desire to scratch

147
Q

What nerve fibres sense the itch sensation

A

Unmyelinated C fibres

148
Q

Where in the brain is the itch sensation processed

A

Parts of the forebrain and hypothalamus

149
Q

How is information on itch conveyed

A

Centrally in 2 separate systems that use the lateral spinothalamic tract

150
Q

Pruritoceptive itch

A

Something in skin triggers the itch

151
Q

Neuropathic itch

A

Damage to central or peripheral nerves causes an itch

152
Q

Neurogenic itch

A

No evident damage in CNS, but itch caused by e.g. opiate effects on CNS receptors

153
Q

Name some systemic diseases associated with itch

A

Haematological, paraneoplastic, liver and bile duct, kidney disease, thyroid issues

154
Q

Psychogenic itch

A

Psychological causes with no CNS damage

155
Q

Name some non-specific anti-itch treatments

A

Sedative anti-histamines
Emollients
Antidepressants
Anti-epileptics for neuropathic itch
Phototherapy

156
Q

When does skin aging usually occur from

157
Q

What occurs during skin aging (4)

A

Skin becomes thinner
Subcutaneous fat is lost
Fine wrinkles develop
Number of hair follicles etc. reduce and skin becomes dry

158
Q

What is solar elastosis

A

Degeneration and clumping of elastin fibres in the dermis as a result of chronic exposure to UV radiation

159
Q

How does the skin appear in solar elastosis

A

Yellow-brownish hue, wrinkles

160
Q

Difference between a food allergy and intolerance

A

Allergy is IgE mediated, intolerance is a non-immune reaction

161
Q

Effect of obesity on collagen structure and function and wound healing

A

Reduced mechanical strength due to failure of collagen deposition to match the increased surface area

162
Q

Effect of obesity on sebaceous glands

A

Increased androgens produced in peripheral fat stimulate glands leading to acne

163
Q

Effect of obesity on subcutaneous fat

A

Increased hormone production e.g. testosterone

164
Q

Effect of obesity on lymphatics

A

Pressure from fat stops flow and causes leakage into subcutaneous tissues

165
Q

Effects of obesity on circulation

A

Microvascular dysfunction resulting in increased skin blood flow - may contribute to hypertension

166
Q

Effect of obesity on apocrine and eccrine glands

A

Increased activity in skin folds increases moisture
Maceration and friction increases irritation

167
Q

Effect of obesity on barrier function of the skin

A

Increased trans-epidermal water loss so skin tends to be dry

168
Q

What is acanthosis nigricans associated with

A

Insulin resistance

169
Q

What is acanthosis nigricans

A

Velvety thickening and pigmentation of skin folds

170
Q

Where is acanthosis nigricans usually seen

A

In the axilla

171
Q

What is hidradenitis suppurative

A

Chronic inflammatory disease where boils and abscesses form and scar apocrine gland areas

172
Q

What is hidradenitis suppurative associated with

A

Hyper-androgenism

173
Q

What is intertrigo

A

Macerated red plaques which develop in skin folds due to high moisture levels, friction, increased pH and reduced barrier function

174
Q

What kind of psoriasis is aggravated by obesity

175
Q

What are keratinocytes

A

The structural and functional cells of the epidermis

176
Q

Roles of keratinocytes

A

Produce antimicrobial peptides to kill pathogens
Produce cytokines and chemokines

177
Q

What are langerhans cells characterised by

A

Birbeck granules

178
Q

What is the main type of T cell found in the epidermis

A

CD8+ T cells

179
Q

What is an Arthus reaction

A

Localised vasculitis associated with deposition of immune complexes and activation of complement

180
Q

Name the 2 types of dendritic cells found in the dermis

A

Dermal and plasmacytoid

181
Q

Role of dermal dendritic cells

A

Involved in antigen presenting and secreting cytokines and chemokines

182
Q

Role of plasmacytoid dendritic cells

A

Produce INFalpha, found in diseased skin

183
Q

Role of class I MHC

A

Present endogenous antigens to cytotoxic T cells

184
Q

Role of class II MHC

A

Present exogenous antigens to Th cells

185
Q

Role of TNFalpha

A

Mediated communication between T cells and macrophages

186
Q

What secretes IL17

A

Th17 cells

187
Q

Role of IL17

A

Activates keratinocytes and fibroblasts

188
Q

What secretes IL23

A

Dendritic cells and macrophages

189
Q

Role of IL23

A

Triggers differentiation and growth of Th17 cells

dermatology (13 decks)

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