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DERMATOLOGY > Structure and Function > Flashcards

Structure and Function Flashcards

1
Q

Roughly how many skin diseases are known?

A

> 2000

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2
Q

Describe the difference between the EPIDERMIS and the DERMIS

A

Epidermis = outer layer of stratified squamous epithelium

Dermis = below epidermis, made of connective tissue, often described as “leather”

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3
Q

In terms of embryology, where does the epidermis come from?

A

the ectoderm

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4
Q

In terms of embryology, where does the dermis come from?

A

The mesoderm

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5
Q

What part of the embryo do melanocytes (pigment cells) come from?

A

The neural crest

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6
Q

What layers of the skin are present at week 4 of foetal development?

A

Periderm
Basal Layer
Dermis

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7
Q

What layers of the skin are present at week 16 of foetal development?

A 
Keratin Layer
Granular Layer
Prickle Cell Layer
Basal Layer
Dermis

melanocytes also migrate from neural crest

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8
Q

What layers of the skin are present at week 26 of foetal development?

A 
Epidermis
Appendages
Dermo-epidermal junction 
Dermis
Subcutis (Fat)
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9
Q

Name the appendages found in the epidermis and dermis of the skin

A

melanocytes
sebaceous gland
hair follicle
arector pili muscle

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10
Q

What is the function of the arector pili muscle in animals?

A

Controls temperature

Muscle contraction allows animal to stand its fur on end to decrease temp

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11
Q

What are Blaschko’s Lines?

A

growth patterns of skin that do not follow nerves/vasculature/lymphatics

e.g if a rash were to start at the nipple and progress down the inner arm

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12
Q

If a patient displays a rash in a developmental pattern, what can be assumed about their condition?

A

It was acquired pre-natally

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13
Q

During what week of foetal development could a mutation occur which causes all cells in a specific section to be affected?

A

Week 11

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14
Q

What type of epithelium is found at the epidermis and how thick is it?

A

Stratified squamous epithelium

~ 1.5 mm thick

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15
Q

What type of cell predominantly makes up the epidermis?

A

95% epidermis = keratinocytes

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16
Q

Name 3 other types of cell found in the epidermis

A

Melanocytes
Langerhans cells
Merkel cells

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17
Q

What is the function of the thick layer of keratin on the surface of the epidermis?

A

Thick layer of keratin = dead skin cells from proliferation

Stops water and bacteria penetrating the skin

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18
Q

Describe the epidermal variation between the scalp, the armpit and the palms of hands/sole of the foot

A 
Scalp = hair, normal amount of sweat glands
Armpit = hair, extra apocrine sweat gland adjacent to hair follicle (produces smell)
Hands/feet = no hair , but extra sweat glands
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19
Q

Give an example of “mechanical trauma” that would cause calluses to develop on the hands

A

playing guitar

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20
Q

Describe the ratio of epidermis to dermis in the skin of the abdomen

A

EPIDERMIS = thin

DERMIS - thick

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21
Q

What 3 factors regulate skin growth?

A

Growth Factors
Cell Death
Hormones

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22
Q

Name conditions where the predominant feature is a loss of control of skin growth

A

Cancer

Psoriasis

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23
Q

What produces the thick scabs in psoriasis?

A

Cells multiply too quickly and skin grows too fast
layer of keratin on surface is larger and does not fall off
=> leaving behind scabs

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24
Q

Where do keratinocytes come from?

A

The basement membrane

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25
Q

How long does it take for cells to migrate from the bottom to top of the epidermis (i.e. regeneration to occur)?

A

28 days

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26
Q

What type of epithelium does the basal membrane have and what thickness is it?

A

Usually one cell thick

Small cuboidal

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27
Q

Where do prickle cells arise from and what are they connected to?

A

Daughter cells of basal cells
Connected to desmosomes
these cells move upwards

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28
Q

Describe the appearance of the granular layer

A

2-3 layers of flatter cells

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29
Q

What proteins, released in the granules, are responsible for forming the ‘cornified envelope’

A

structural filaggrin and involucrin proteins

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30
Q

What is the function of the ‘cornified envelope’?

A

No water OUT (retains moisture in skin)

No bacteria IN (prevents infection)

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31
Q

How do the proteins in the granular layer retain moisture?

A

Large proteins are not req’d therefore they are split into small amino acids which can bind water.

Without this mechanism our skin dries out

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32
Q

What is the largest component of the keratin layer?

A

Corneocytes

overlapping non-nucleated cell remnants

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33
Q

Why is the dermis so large in a wart?

A

The body attempts to proliferate the dermis to push the virus out

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34
Q

Can mucosa also be affected by skin diseases?

A

Yes

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35
Q

What can you deduct from the oral mucosa being white in colour?

A

Blood vessels are no longer visible, therefore the epidermis or dermis must have thickened.

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36
Q

What happens when skin appendages are lost?

A

Scarring

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37
Q

What is scarring made up of?

A

Collagen

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38
Q

What are melanocytes?

A

Pigment producing dendritic cells

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39
Q

Where are melanocytes found?

A

The basal layer and above

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40
Q

What organelles are found inside melanocytes and what is their function?

A

melanosomes

Convert tyrosine to melanin pigment

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41
Q

How is melanin pigment transferred to keratinocytes?

A

via dendrites

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42
Q

How does the border of a melanocyte look histologically?

A

White halo effect

due to water depletion which causes contents of cell to shrink

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43
Q

What is the function of melanin caps?

A

Protect nuclear DNA of basal cells

44
Q

What is vitiligo?

A

autoimmune disease with loss of melanocytes

45
Q

What stimulates melanin production?

A

UV Light

Hormones

46
Q

What is the risk of biochemically stimulating melanocytes?

A

Melanomas can form

47
Q

How many people does Albinism affect in the UK?

A

1:20,000

48
Q

What is albinism?

A

a genetic partial loss of pigment production

49
Q

What hormone is responsible for Nelson’s syndrome?

A

ACTH

produced in excess by pituitary in this condition

50
Q

`Where are Langerhans cells found?

A

Prickle cell level in epidermis

Also found in dermis and lymph nodes

51
Q

Where do Langerhans cells originate from?

A

Mesenchymal origin – bone marrow

52
Q

What role do Langerhans cells play in the immune system?

A

Antigen presenting cells

They pick up antigens in skin and circulate to lymph nodes via lymphatic system

53
Q

What organelle and granules are specific to Langerhans cells?

A

Racket Organelle

Birbeck granules

54
Q

What is the function of Merkel cells?

A

mechanoreceptors

=> can sense if something goes over you

55
Q

Where are merkel cells found?

A

On the ends of myelinated nerves in the basal layer

56
Q

What is notable of Merkel Cell cancer?

A

Rare
Caused by viral infection
High mortality

57
Q

What is a hair follicle always accompanied by?

A

Adjacent sebaceous gland

58
Q

What causes the pigment of hair?

A

melanocytes above dermal papilla

59
Q

What is the side effect of retinoids given to treat acne?

A

They block formation of sebum => can create very dry skin

60
Q

Name the three phases of hair growth

A 
Anagen 	=  growing
Catagen 	=  involuting
Telogen   	=  resting
61
Q

How does the hair follicle develop embryologically?

A

Buds from the epidermis downwards

62
Q

What hormones can influence hair growth?

A

Thyroxine and androgens

63
Q

What drugs can cause a synchronous Telogen phase? (aka all hair beginning to fall out at the same time)

A

Chemotherapy & Radiotherapy

64
Q

What causes alopecia areata?

A

Autoimmune condition where the hair follicles are attacked by T-lymphocytes

65
Q

How much do nails grow each day?

A

Growth rate 0.1mm per day

Fingers > toes
Summer > winter

66
Q

How are the stem cells which make up our nail, different to that which make up the rest of the skin layers?

A

They differentiate into keratin which is aligned into a parallel sheath

67
Q

Which part of the nail is responsible for severe pain during trauma to the nail?

A

Nail matrix

68
Q

What is the main function of the dermo-epidermal junction?

A

Support / anchorage / adhesion

growth and differentiation of basal cells

69
Q

What can happen if the dermo-epidermal junction is not intact?

A

skin can slip/blister/fail

70
Q

What are the layers of the dermo-epidermal junction?

A

Lamina lucida
Lamina densa
Sub-Lamina densa

71
Q

Give an example of a condition where failure of the dermo-epidermal junction causes blistering

A

Bullous Pemphigoid

72
Q

If a person produces antibodies to their own dermo-epidermal junction, what test can we use to detect these/

A

Immunofluorescence

73
Q

Give an example of a condition where there is a structural protein complex mutation in the dermo-epidermal junction

A

Epidermolysis Bullosa

(in babies)

74
Q

What symptoms can Epidermolysis Bullosa cause?

A

Widespread blistered, red and crusted skin

oesophageal strictures => feeding problems

Nailbeds are absorbed

Hands are fused (mitten deformities)

75
Q

What cells are found in the dermis?

A 
fibroblasts                                  	 
macrophages 
mast cells
lymphocytes
Langerhans cells
76
Q

What do fibroblasts in the dermis make?

A

Collagen and elastin

77
Q

What 3 things can give you fewer elastic fibres in your skin?

A

Ageing
UV light
smoking

78
Q

Why do we have way more blood vessels in our skin that we require for only nutrition?

A 
Temperature regulation
(vasoconstriction/vasodilation)
79
Q

How are blood vessels in the skin arranged?

A

Horizontal plexuses

80
Q

What is an angioma?

A

a benign overgrowth of blood vessels showing through the epidermis and dermis

81
Q

How are lymphatic vessels in the skin arranged?

A

Sub-epidermal horizontal plexus (like blood vessels)

82
Q

What is cellulitis?

A

Bacterial infection of lymphatics

83
Q

What specialised receptors are present in the skin

A

Pacinian (pressure) and Meissners (vibration) corpuscles

84
Q

What condition can occur as a result of nerve overgrowth?

A

Neurofibromatosis

85
Q

Name the three types of skin glands

A

Sebaceous
Apocrine
Eccrine

86
Q

Where are sebaceous glands found and what is their function?

A

largest glands face and chest

Functions:
control moisture loss
protection from fungal infection

87
Q

Where are apocrine glands found and what do they produce?

A

Axillae and perineum

Androgen dependent

Produce oily fluid (odour after bacterial decomposition)

88
Q

Where are eccrine glands found and what is their function?

A

Whole skin surface
(palms, soles and axillae in particular)

Functions:
cooling by evaporation
moisten palms / soles to aid grip

89
Q

What are the main functions of the skin?

A 
Barrier
Metabolism & detoxification
Temp. reg.
Immune defence
Sensory
90
Q

Give 2 examples of acute skin failure

A

Toxic epidermal necrolysis
Erythroderma
`

91
Q

What consequences are there if the skin fails and therefore doesnt work as a BARRIER?

A

Fluid loss => Dehydration
Protein loss => Hypoalbuminaemia
Infection

92
Q

What consequences are there if the skin fails and therefore deosnt work to regulate heat?

A

Heat loss => Hypothermia

93
Q

What consequences are there if the skin fails and cant function as an immune defence?

A

Spread of infection

94
Q

What consequences occur if the skin fails metabolically?

A

Disordered thyroxine metabolism

95
Q

What consequences can occur if the skin fails and loses its sensory function?

A

Pain sensation

96
Q

What 3 categories does the skin protect us from as a BARRIER?

A

Physical

  • Friction, mechanical trauma
  • Ultraviolet radiation

Chemical
- Irritants, allergens, toxins

Pathogens
- Bacteria, viruses, fungi

97
Q

How does the skin not split when you hit your hand off of a table for example?

A

The subcutaneous layer dissipates the energy

98
Q

Give examples of everyday items that could be responsible for Cumulative irritant hand dermatitis

A

Rings

Soap/washing up liquid

99
Q

If an ulcer were to develop following a compound fracture, what is the patient at risk of now that the compound is exposed?

A

Osteomyelitis

infection of the bone

100
Q

Give 2 examples of how the skin is metabolically active

A

Vitamin D metabolism

Thyroid hormone metabolism

101
Q

In what ways can our skin regulate our temperature?

A

Control sweating
shivering
Vasoconstrict/ vasodilate blood supply

102
Q

How many scabies mites can usually be found on an average infected patient?

A

12

103
Q

How many scabies mites can be found if the skin is crusting?

A

Millions!

104
Q

Describe the type of inflammation and its location in Tuberculoid leprosy (Hansen’s Disease)

A

Granulomatous inflammation to wall off an infection in the dermis

105
Q

What percentage of patients with Chronic discoid lupus erythematosus will progress to having SLE?

A

10%

106
Q

What sensory functions can the skin perform?

A

Touch, pressure, vibration
Pain and itch
Heat and cold
Nerve endings and receptors in skin

107
Q

What other condition is linked to Neuropathic ulcers(leprosy)?

A

Diabetes Mellitus

DERMATOLOGY (18 decks)

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