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Dermatology > Physiology of the skin > Flashcards

Physiology of the skin Flashcards

1
Q

Epidermis

A

Outer layer - stratified cellular epithelium

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2
Q

Dermis

A

Connective tissue

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3
Q

Functions of the skin

A

Metabolism & detoxification
Thermoregulation
Immune defence
Sociosexual /Sensory functions

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4
Q

Blaschko’s lines

A

Developmental growth pattern of skin – not following vessels, nerves or lymphatics

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5
Q

What is the skin made up of?

A 
Epidermis
Appendages: Nails, Hair, Glands, Mucosae
Dermo-epidermal junction
Dermis: connective tissue, less cellular 
Subcutaneous: predominantly fat
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6
Q

Predominant cell of the epidermis

A

Keratinocytes

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7
Q

Regulation of epidermal turnover

A

Growth factors
Cell death
Hormones

Loss of control in:
Skin cancer
Psoriasis

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8
Q

Layers of epidermis - top to bottom

A

Keratin
Granular
Prickle cell
Basal

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9
Q

Corneocytes

A

Differentiated keratinocytes in keratin layer

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10
Q

Melanocytes

A

Pigment producing cells from neural crest

basal layer and above

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11
Q

Eumelanin

A

brown or black

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12
Q

Phaeomelanin

A

Red, yellow

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13
Q

Vitiligo

A

Autoimmune disease with loss of melanocytes (white and black skin both present)

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14
Q

Albinism

A

A genetic partial loss of pigment production

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15
Q

Nelson’s syndrome

A

Melanin stimulating hormone is produced in excess by the pituitary

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16
Q

Malignant melanoma

A

A tumour of the melanocyte cell line

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17
Q

Langerhans cells

A

Antigen presenting cells

Pick up antigen in skin and circulate to lymph nodes via lymphatic system

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18
Q

Merkel cells

A

Mechanoreceptors

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19
Q

Pilosebaceous unit

A

Hair follicles
Found in both layers of dermis and epidermis
Adjacent sebaceous gland
Hair pigmentation via melanocytes above dermal papilla

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20
Q

Anagen

A

Growing - takes 3-7 years (90% of hairs)

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21
Q

Catagen

A

Involuting (10% of hairs – 3-4 weeks)

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22
Q

Telogen

A

Resting – shedding phase daily – 50-100 hairs (<1%)

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23
Q

Telogen effluvium

A

A form of temporary hair loss that usually happens after stress, a shock, or a traumatic event. Different from the permanent hair loss disorder called alopecia areata.

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24
Q

Virilisation

A

Due to excess androgen from a tumour (male pattern of hair growth on females e.g. beard)

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25
Q

Alopecia areata

A

Autoimmune hair loss – attacking of hair follicles

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26
Q

Dermo- epidermal Junction

A

Interface between epidermis and dermis

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27
Q

Function of the Dermo- epidermal Junction

A

Key role in epithelial–mesenchymal interactions:
Support, anchorage, adhesion, growth and differentiation of basal cells
Semi-permeable membrane acting as barrier and filter

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28
Q

Collagen function

A

Provides tensile strength and elastic properties of skin

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29
Q

Bullous pemphigoid

A

An autoimmune pruritic skin disease preferentially in older people, aged over 60, that may involve the formation of blisters (bullae) in the space between the epidermal and dermal skin layers.

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30
Q

Bullous pemphigoid antibodies

A

Anti-hemidesmosome antibodies

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31
Q

Epidermolysis bullosa

A

A rare genetic condition that makes skin so fragile that it can tear or blister at the slightest touch. Children born with it are often called “Butterfly Children” because their skin seems as fragile as a butterfly wing. Mild forms may get better with time.

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32
Q

Photoaging

A

The dermis contains collagen, elastin, and other important fibres, that affect the skin’s strength and elasticity and are responsible for skin’s smooth, youthful appearance.

Photoaging refers to skin damage caused by prolonged sun exposure and can lead to skin cancers.

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33
Q

Special sensory skin nerves

A

Pacinian (pressure)

Meissner’s (vibration) corpuscles

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34
Q

Pacinian receptors

A

For pressure (sensory nerves)

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35
Q

Meissner’s corpuscles

A

For vibration (sensory nerves)

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36
Q

Three types of skin glands

A

Sebaceous
Apocrine
Eccrine

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37
Q

Sebaceous glands

A

Largest glands face and chest
Produce sebum
Functions: control moisture loss & protection from fungal infection

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38
Q

Apocrine glands

A

Function unknown
Develop as part of pilosebaceous unit
Axillae, perineum and genitals – develop at puberty and open into hair follicles
Produce oily fluid - odour after bacterial decomposition

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39
Q

Eccrine glands

A

Whole skin surface – not found on lips or genitals

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

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40
Q

The keratin layer/epidermis

A

Tough, lipid rich, physical barrier.

Formed by terminal differentiation of keratinocytes to corneocytes.

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41
Q

Keratinocytes (KC) in the epidermis

A
  1. Sense pathogens via cell surface receptors
  2. Produce antimicrobial peptides that directly kill pathogens.
  3. Produce cytokines and chemokines.
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42
Q

What disease is TH1 cells associated with?

A

Psoriasis

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43
Q

What disease is TH2 cells associated with?

A

Atopic dermatitis

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44
Q

What disease is TH17 cells associated with?

A

Psoriasis and atopic dermatitis

45
Q

Different types of dendritic cell (DC) found in the dermis

A
  1. Dermal

2. Plasmacytoid

46
Q

Dermal dendritic cells

A

Involved in Ag presenting and secreting cyto/chemokines

47
Q

Plasmacytoid dendritic cells

A

Produce IFNα. Found in diseased skin

48
Q

Neutrophils

A

Circulating leukocytes attracted to tissue by chemokines (chemoattractant)

49
Q

Mast Cells

A

Effectors of IgE-mediated immune response (allergy) – type I hypersensitivity reactions

Binding of IgE causes activation of the mast cell & release of inflammatory mediators: Tryptase, chymase, TNF, histamine

50
Q

Class I MHC

A

o Found on almost all cells
o Present Ag to cytotoxic T cells
o Present endogenous Ag

51
Q

Class II MHC

A

o Found on APC (B cells, macrophages)
o Present to TH cells
o Present exogenous Ag

52
Q

Secondary (acquired) immunodeficiency diseases

A
  1. AIDS
  2. Malignancy
  3. Aging
  4. Diabetes, renal malfunction, burns, alcoholic cirrhosis, malnutrition
53
Q

Type I (immediate) hypersensitivity (Allergy)

A

Antibody mediated: IgE.

Early exposure to allergen causes the production of IgE, which binds to FcεR1 receptor on mast cells. Later exposure causes rapid crosslinking of the receptors, signal transduction and degranulation of the mast cell.

54
Q

Type II hypersensitivity reaction

A

Refers to an antibody mediated immune reaction in which antibodies IgG and IgM are directed against cellular or extracellular matrix antigens with resultant cellular destruction, functional loss, or damage to tissues

55
Q

Type III hypersensitivity reactions

A

An abnormal immune response is mediated by the formation of antigen-antibody aggregates called immune complexes

56
Q

Arthus reaction

A

A type of local type III hypersensitivity reaction - involve the deposition of antigen/antibody complexes mainly in the vascular walls, serosa, and glomeruli.

57
Q

Type IV hypersensitivity

A

Called delayed type hypersensitivity as the reaction takes several days to develop. Unlike the other types, it is not antibody-mediated but rather is a type of cell-mediated response. This response involves the interaction of T cells, monocytes, and macrophages.

58
Q

Common local side effects of drugs applied to the skin

A 
Superficial skin disorders e.g psoriasis & eczema
Skin infections
Itching
Dry skin
warts
59
Q

Pruritis

60
Q

Glucocorticoids

A

Possess anti-inflammatory, immunosuppressant and vasoconstricting effects plus anti-proliferating action upon keratinocytes and fibroblasts

61
Q

Skin failure consequences

A
  1. Loss of thermo-regulation
  2. Increased risk of infection
  3. Failure of homeostatic function - enormous fluid losses and may lead to cardiovascular dysfunction
62
Q

First degree burns

A

Epidermis only.

63
Q

Second degree burns

A

Second degree/Partial thickness: epidermis and dermis.

64
Q

Third degree burns

A

Third degree/ Full thickness: extends beyond dermis.

65
Q

Chronic wounds

A

(Present for >6 weeks) don’t heal in the normal orderly stages.

Most common chronic wounds are leg ulcers, usually due to underlying vascular problems (arterial insufficiency, venous stasis, or a mixture of both).

66
Q

Purpura (colour)

A

Due to extravasation (leakage of fluids from a vein) of blood, will not blanche, may be raised

67
Q

Petechia

A

Smaller 1-2mm area of purpura

68
Q

Erythema

A

Due to vascular dilatation, will blanche on pressure

69
Q

Macule

A

< 1cm flat lesion

70
Q

Patch

A

> 1cm FLAT lesion

71
Q

Papule

A

< 0.5cm raised lesion

72
Q

Nodule

A

> 0.5cm raised lesion

73
Q

Plaque

A

Raised edge but flatter surface

74
Q

Wheal

A

Compressible dermal swelling

75
Q

Vesicle

A

< 0.5cm fluid-filled lesion

76
Q

Bulla

A

> 0.5cm fluid-filled lesion

77
Q

Cyst

A

Is a nodule (> 0.5cm raised lesion) containing semi-solid material

78
Q

Pustule

A

Pus filled

79
Q

Scale

A

Accumulated fragments of keratin layer

80
Q

Crust

A

Dried exudate e.g serum

81
Q

Lichenified

A

Skin thickening with increased skin markings

82
Q

Scar

A

Normal tissue replaced by fibrous tissue

83
Q

Erosion

A

Superficial break in epidermis

84
Q

Ulcer

A

Deeper break in epidermis

85
Q

Fissure

A

Linear split in epidermis

86
Q

Atrophy

A

Loss of epidermis +/- dermis but surface remains intact

87
Q

Examples of Type I ( immediate) hypersensitivity reactions

A

Urticaria
Angio-oedema
Anaphylaxis

88
Q

Examples of Type IV ( immediate) hypersensitivity reactions

A

Allergic contact dermatitis
Photo-allergy
Skin response to bacteria, fungi, viruses.

89
Q

Patch testing

A

Useful skin test to identify contact allergens (type IV hypersensitivity)

90
Q

Which two reaction types are most commonly seen in the skin?

A

Type I and Type IV

91
Q

Systemic side effects of glucocorticoids

A
  1. Suppression of HPA axis
  2. Cushing’s disease (rare)
  3. Growth retardation (extremely rare)
92
Q

The 2 categories for food hypersensitivity

A
  1. Immune mediated (food allergy)

2. Non-immune mediated reactions (food intolerance).

93
Q

The 2 categories for food allergy

A
  1. IgE-mediated (immediate onset) ‘

2. Non-IgE mediated (delayed onset).

94
Q

Most common food allergens

A 
Cow’s milk
Chicken egg
Fish
Shellfish especially prawns, 
Soya 
Peanuts
Tree nuts
Wheat
95
Q

Prick test

A

Intradermal injection of suspected substance e.g. latex. Look for wheal and flare reaction within 30mins.

96
Q

Calcineurin Inhibitors

A
  • Tacrolimus, pimecrolimus

* Suppress lymphocyte activation

97
Q

Antifungal creams

A

Clotrimazole,
Terbinafine
Ketoconazole

98
Q

Keratolytics

A

Used to soften keratin e.g salicylic acid

99
Q

Hyperkeratosis

A

Increased thickness of keratin layer

100
Q

Parakeratosis

A

Persistence of nuclei in keratin layer

101
Q

Acanthosis

A

Increased thickness of epithelium

102
Q

Papillomatosis

A

Irregular epithelial thickening

103
Q

Examples of Type II hypersensitivity reactions

A

Pemphigus & pemphigoid

104
Q

Examples of Type III hypersensitivity reactions

A

Purpura/rash

105
Q

Fitzpatrick classification

A

The classification of skin type, known as the Fitzpatrick skin type (or photo-type), depends on the amount of melanin pigment in the skin

106
Q

Vitamin D

A

A fat-soluble pro-hormone essential for calcium and phosphorus metabolism.

107
Q

Actinic lentigines

A
  • Actinic or solar lentigines (singular lentigo)
  • Also known as ‘age’ or ‘liver’ spots
  • Related to UV exposure
108
Q

Freckles

A
  • Patchy increase in melanin pigmentation
  • Occurs after UV exposure
  • Most common in fair skinned and red heads

Dermatology (4 decks)

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