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Medicine Dermatology > Structure and Function > Flashcards

Structure and Function Flashcards

1
Q

What epithelium forms the epidermis?

A

Stratified squamous epithelium

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2
Q

What is the dermis?

A

A layer of connective tissue beneath the epidermis

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3
Q

Which embryological layer forms the epidermis?

A

Ectoderm

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4
Q

Which embryological layer forms the dermis?

A

Mesoderm

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5
Q

Foetal skin development:

  • 4 weeks
  • 16 weeks
  • 26 weeks
A

4 weeks - periderm, basal layer, dermis
16 weeks - keratin layer, granular layer, prickle cell layer, basal layer, dermis
26 weeks - epidermis

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6
Q

Blaschko’s lines

A

Developmental growth pattern of the skin. Anything wrong with the skin at birth will follow these lines. If something runs along these lines it is a genetic error

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7
Q

What does the skin consist of?

A

Epidermis, appendages, dermo-epidermal junction, dermis, sub-cutis

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8
Q

Appendages

A

Nails, hair, glands, mucosae

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9
Q

What forms a scar?

A

The appendages no longer being present

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10
Q

Function of sebaceous gland

A

Secrete grease

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11
Q

Function of erector pili muscle

A

Causes hairs to erect

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12
Q

Pilosebaceous unit

A

Consists of the hair shaft, the hair follicle, the sebaceous gland and the erector pili muscle

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13
Q

Which cell makes up 95% of the epidermis?

A

Keratinocytes - contain structural keratins

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14
Q

Layers of the epidermis

A

Keratin layer, granular layer, prickle cell layer, basal layer

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15
Q

Cells of the epidermis and where they are found

A

Keratinocytes - keratin layer
Melanocytes - basal and suprabasal layers
Langerhans cells - suprabasal layer
Merkel cells - basal layer

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16
Q

Things that control the regulation of epidermal turnover

A

Growth factors, cell death, hormones

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17
Q

Conditions where there is loss of control in regulation of epidermal turnover

A

Skin cancer and psoriasis

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18
Q

How long does it take from keratinocytes to travel from the bottom to the top of the epidermis?

A

28 days

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19
Q

How many cells thick is the basal layer?

A

One

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20
Q

What shape are the cells in the basal layer?

A

Small cuboidal cells

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21
Q

What is there lots of in the basal layer?

A

Intermediate filaments (keratin)

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22
Q

The basal layer is highly metabolically active - true or false?

A

True

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23
Q

Describe the shape of cells in the prickle layer

A

Larger polyhedral cells

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24
Q

What are there lots of in the prickle cell layer?

A

Desmosomes

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25
Q

What are desmosomes?

A

Cell to cell contacts which allow both adhesion (to impart stability) and flexibility (so cells can move upwards)

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26
Q

How many layers of cells are there in the granular layer?

A

2-3 layers of flatter cells

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27
Q

What does the granular layer contain?

A

Large keratohyalin granules, odland bodies and a high lipid content

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28
Q

What do keratohyalin granules contain?

A

Structural fillagrin and involucrin proteins

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29
Q

Where is the origin of the cornified envelope?

A

Granular layer

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30
Q

Describe cell nuclei in the granular layer

A

Cell nuclei are lost

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31
Q

Where are corneocytes found?

A

Keratin layer

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32
Q

What are corneocytes?

A

Terminally differentiated keratinocytes and compose most if not all of the stratum corneum. They are ‘dead’ cells

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33
Q

Which layer, other than the granular layer, is part of the cornified envelope?

A

Keratin layer

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34
Q

Function of the keratin layer

A

Provides a waterproof barrier to the skin and releases lamellar granules

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35
Q

Example of disease affecting keratinocytes

A

Human papilloma virus of keratinocyte causes warts

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36
Q

Oral mucosa

A 
Masticatory (keratinised to deal with friction/pressure)
Lining mucosa (non-keratinised)
Specialised mucosa (tongue papillae - taste)
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37
Q

Ocular mucosa

A

Lacrimal glands, eyelashes, sebaceous glands

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38
Q

When are melanocytes formed in human development?

A

Within the first 3 months of development

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39
Q

Where are melanocytes formed in human development?

A

Migrate from neural crest to epidermis

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40
Q

In what layer of skin are melanocytes formed?

A

Basal layer and above

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41
Q

What are melanocytes?

A

Pigment producing dendritic cells

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42
Q

Which organelles do melanocytes contain?

A

Melanosomes

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43
Q

Function of melanosomes

A

Convert tyrosine to melanin pigment

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44
Q

Colour of eumelanin

A

Brown or black

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45
Q

Colour of phaeomelanin

A

Red, yellow

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46
Q

What drives the conversion of tyrosine to melanin pigment?

A

The hormone alpha MSH - part of ACTH

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47
Q

Function of melanin

A

Absorbs light. It is a natural density filter

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48
Q

What are full melanosomes (melanin granules) transferred from the adjacent keratinocytes via?

A

Dendrites

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49
Q

Why do melanosomes form a cap over the nucleus?

A

To protect stem cells from DNA mutations

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50
Q

Briefly describe the following conditions:

  • Vitiligo
  • Albinism
  • Nelson’s syndrome
  • Melanoma
A

Vitiligo - autoimmune disease disease with loss of melanocytes
Albinism - genetic partial loss of pigment production
Nelson’s syndrome - melanin stimulation hormone is produced in excess by the pituitary
Melanoma - tumour of the melanocyte cell line

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51
Q

What type of cells are Langerhan’s cells?

A

Dendritic cells

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52
Q

Where do Langerhan’s cells originate?

A

Mesenchymal origin - bone marrow

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53
Q

Where are Langerhan’s cells found?

A

Prickle cell level in the epidermis, dermis and lymph nodes

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54
Q

Describe Langerhan’s cells in the immune system

A

They are antigen presenting cells. They pick up the antigen in skin and circulate to lymph nodes via lymphatic system

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55
Q

Function of Merkel cells

A

Detect pressure and transmit touch to the brain

56
Q

What type of receptors are Merkel cells?

A

Mechanoreceptors

57
Q

Where are Merkel cells found?

A

They are basal cells, found between keratinocytes and nerve fibres

58
Q

What causes Merkel cell cancer?

A

Viral infection

59
Q

True or false: Merkel cell cancer has a low mortality

A

False - it has a high mortality

60
Q

Phases of growth of hair

A

Anagen - growing
Catagen - involuting
Telogen - resting

61
Q

Types of hair

A

Lanugo (in utero), vellus, terminal

62
Q

What makes hair?

A

Specialised keratins

63
Q

What is hair pigmentation via?

A

Melanocytes above dermal papilla

64
Q

What makes nails?

A

Specialised keratins

65
Q

2 parts of the dermis

A

Papillary dermis at the top and reticular dermis

66
Q

Dermo-epidermal junction

A

Interface between the epidermis and dermis

67
Q

What makes up the dermo-epidermal junction?

A

Lamina lucida, lamina densa, sub-laminal densa zone

68
Q

Key roles of dermo-epidermal junction

A

Key role in epithelial-mesenchymal interactions - support, anchorage, adhesion, growth and differentiation of basal cells

69
Q

Who does bullous pemphigoid tend to affect?

A

The elderly

70
Q

What does bullous pemphigoid destroy?

A

Part of the dermo-epidermal junction

71
Q

What technique can show the dermo-epidermal junction?

A

Immunofluoresence

72
Q

Who gets epidermolysis bullosa?

A

It is very rare but common in babies

73
Q

What is epidermolysis bullosa due to?

A

Various abnormalities in proteins in dermo-epidermal junction

74
Q

Ground substance in the dermis

A

Supportive water-base substance

75
Q

Cells present in the dermis

A

Mainly fibroblast – make a lot of dermis constituents e.g. collagen and elastic fibres
Macrophages
Mast cells
Lymphocytes

76
Q

Fibres present in the dermis

A

Collagen and elastin

77
Q

Which fibre is most abundant in the dermis - collagen or elastin?

A

Collagen - 90% of dermis is collagen based

78
Q

What is lost in photoageing?

A

Elastic fibres

79
Q

Angioma

A

Dilated abnormal blood vessels in the top of the skin - genetic

80
Q

Chronic lymphoedema

A

Lymphatic channels so delicate they can be damaged by infection or trauma. Very difficult to manage. Causes swelling in bodies tissues

81
Q

Dermatomes

A

Somatic sensory nerves in the dermis

82
Q

Special receptors in the dermis

A

Pacinian - detect pressure

Meissners corpuscles - detect vibration

83
Q

What do pacinian receptors look like histologically?

A

Look like onion rings

84
Q

What does the autonomic nerve supply innervate in the dermis?

A

Blood vessels, nerves, glands and supply sweat glands

85
Q

Neurofibromatosis

A

Rareish genetic condition which causes a multiple overgrowth of nerve tissues

86
Q

Acne is a disease of what?

A

Pilosebaceous unit

87
Q

Pigmentation of hair follicles

A

Melanocytes above dermal papilla

88
Q

What is hair made up of?

A

Specialised keratins, adjacent to sebaceous gland

89
Q

Mode of secretion of sebaceous glands

A

Holocrine secretion into pilary canal

90
Q

Where are sebaceous glands present?

A

Face, chest, (upper back)

91
Q

True or false: sebaceous glands are hormone sensitive

A

True - they are quiescent until puberty

92
Q

What do sebaceous glands produce?

A

Sebum: squalene, wax esters, TG and FFA

93
Q

Functions of sebaceous glands

A

Control moisture loss, protect from fungal infection

94
Q

Where are apocrine glands found?

A

Axillae and perineum (and nipples)

95
Q

What do apocrine glands develop as part of?

A

Pilosebaceous unit

96
Q

Apocrine glands are ___ dependent

97
Q

What do apocrine glands produce?

A

Oily fluid that causes odour after bacterial decomposition

98
Q

Most common form of sweat gland

A

Eccrine glands

99
Q

Where are eccrine glands found?

A

All over the skin surface, particularly the palms of hands and soles of feet, facial skin and axillae

100
Q

Nerve supply to the eccrine glands

A

Sympathetic cholinergic

101
Q

Types of stimulation of the eccrine glands

A

Mental stimulation
Thermal stimulation
Gustatory stimulation

102
Q

Describe the shape of the structure of eccrine glands

A

Coiled tubular structures

103
Q

Functions of eccrine glands

A

Cooling by evaporation

Moistens palms/soles to aid grip

104
Q

Functions of the skin

A 
Protective barrier
Thermoregulation
Waterproof barrier
Metabolism and detoxification
Sensory function
Communication
105
Q

Physical barrier functions of the skin

A

Protection against friction, mechanical trauma and UV radiation (UVA (particularly damaging), UVB)

106
Q

Chemical barrier functions of the skin

A

Protection against irritants, allergens and toxins

107
Q

Pathogen protection functions of the skin

A

Protect against bacteria, fungi and metabolism

108
Q

Metabolism of which things occur in the skin?

A

Vitamin D and thyroid hormone

109
Q

2 main ways of getting vitamin D

A

Through the skin or the diet

110
Q

Briefly describe vitamin D metabolism

A

7-dehydrocholesterol → vitamin D3 by UVB

111
Q

What percentage of thyroid hormone metabolism occurs in the thyroid gland vs peripheral tissues (incl. skin)

A

Thyroid gland = 20%

Peripheral tissues = 80%

112
Q

Immune defence is important in…

A

Protection against infection, sunlight responses and allergic reactions

113
Q

Cells involved in the immune defence in the skin

A

Langerhans cells and T cells

114
Q

Ways of communication through skin

A

Visual, odour, sociosexual behaviour

115
Q

Sensory functions of the skin

A

Feel touch, vibration, pressure, pain and itch, heat and cold via nerve endings and receptors in skin

116
Q

Consequence of failure of barrier function of the skin

117
Q

Consequence of fluid loss by the skin

A

Dehydration

118
Q

Consequence of protein loss by the skin

A

Hypoalbuminaemia

119
Q

Consequence of failure of thermoregulation by the skin

A

Heat loss leads to hypothermia

Heat gain leads to hyperthermia

120
Q

Consequence of failure of immune defence of skin

A

Spread of infection

121
Q

Consequence of failure of metabolic function of skin

A

Disordered thyroxine metabolism

122
Q

Consequences of failure of communication function of skin

A

Inability to display healthy skin leading to stigma

123
Q

Basic tissue types in the skin

A

Epithelium, glands, muscle, hair, adipose, connective, nervous, nails

124
Q

Describe epidermis of palm

A

Thick keratin layer and undulations follow those of underlying dermis giving ridges and grooves of fingerprints

125
Q

Describe epidermis of sole of foot

A

Thick keratin layer and the helical structures within this layer are terminal parts of sweat ducts

126
Q

Muscle fibres in the skin

A

Smooth muscle fibres, connective tissue, nervous tissue

127
Q

Function of smooth muscle fibres in the skin

A

Attached to hair follicles (arrector pili) and can pull the hair perpendicular to the skin during cold/fright (goose bumps)
Also present in the walls of blood vessels

128
Q

Function of collagen and elastic fibres in the skin

A

Collagen fibres and elastic fibres are present in the dermis and provide tensile strength and elastic qualities of skin

129
Q

What types of keratin are the following:

  • Central medulla of hair
  • Outer cortex of hair
A

Central medulla = soft keratin

Outer cortex = hard keratin

130
Q

What does the matrix region of hair contain?

A

Keratin producing cells

131
Q

What does the papilla of the hair contain?

A

Multiple vascular channels

132
Q

What are nails?

A

Plates filled with hard keratin

133
Q

Where does the nail plate sit?

A

On the nail bed

134
Q

What happens in the nail matrix?

A

Cells divide and produce hard keratin

135
Q

What is the nail cuticle?

A

Extension of skin fold covering the nail root

136
Q

Function of the hyponychium

A

Secures the free nail edge

Medicine Dermatology (19 decks)

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