Physiology of the skin Flashcards
(108 cards)
1
Q
Epidermis
A
Outer layer - stratified cellular epithelium
2
Q
Dermis
A
Connective tissue
3
Q
Functions of the skin
A
Metabolism & detoxification
Thermoregulation
Immune defence
Sociosexual /Sensory functions
4
Q
Blaschko’s lines
A
Developmental growth pattern of skin – not following vessels, nerves or lymphatics
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
6
Q
Predominant cell of the epidermis
A
Keratinocytes
7
Q
Regulation of epidermal turnover
A
Growth factors
Cell death
Hormones
Loss of control in:
Skin cancer
Psoriasis
8
Q
Layers of epidermis - top to bottom
A
Keratin
Granular
Prickle cell
Basal
9
Q
Corneocytes
A
Differentiated keratinocytes in keratin layer
10
Q
Melanocytes
A
Pigment producing cells from neural crest
basal layer and above
11
Q
Eumelanin
A
brown or black
12
Q
Phaeomelanin
A
Red, yellow
13
Q
Vitiligo
A
Autoimmune disease with loss of melanocytes (white and black skin both present)
14
Q
Albinism
A
A genetic partial loss of pigment production
15
Q
Nelson’s syndrome
A
Melanin stimulating hormone is produced in excess by the pituitary
16
Q
Malignant melanoma
A
A tumour of the melanocyte cell line
17
Q
Langerhans cells
A
Antigen presenting cells
Pick up antigen in skin and circulate to lymph nodes via lymphatic system
18
Q
Merkel cells
A
Mechanoreceptors
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
20
Q
Anagen
A
Growing - takes 3-7 years (90% of hairs)
21
Q
Catagen
A
Involuting (10% of hairs – 3-4 weeks)
22
Q
Telogen
A
Resting – shedding phase daily – 50-100 hairs (<1%)
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.
24
Q
Virilisation
A
Due to excess androgen from a tumour (male pattern of hair growth on females e.g. beard)
25
Alopecia areata
Autoimmune hair loss – attacking of hair follicles
26
Dermo- epidermal Junction
Interface between epidermis and dermis
27
Function of the Dermo- epidermal Junction
Key role in epithelial–mesenchymal interactions:
Support, anchorage, adhesion, growth and differentiation of basal cells
Semi-permeable membrane acting as barrier and filter
28
Collagen function
Provides tensile strength and elastic properties of skin
29
Bullous pemphigoid
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.
30
Bullous pemphigoid antibodies
Anti-hemidesmosome antibodies
31
Epidermolysis bullosa
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.
32
Photoaging
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.
33
Special sensory skin nerves
Pacinian (pressure)
| Meissner’s (vibration) corpuscles
34
Pacinian receptors
For pressure (sensory nerves)
35
Meissner’s corpuscles
For vibration (sensory nerves)
36
Three types of skin glands
Sebaceous
Apocrine
Eccrine
37
Sebaceous glands
Largest glands face and chest
Produce sebum
Functions: control moisture loss & protection from fungal infection
38
Apocrine glands
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
39
Eccrine glands
Whole skin surface – not found on lips or genitals
| Functions: cooling by evaporation - moisten palms / soles to aid grip
40
The keratin layer/epidermis
Tough, lipid rich, physical barrier.
| Formed by terminal differentiation of keratinocytes to corneocytes.
41
Keratinocytes (KC) in the epidermis
1. Sense pathogens via cell surface receptors
2. Produce antimicrobial peptides that directly kill pathogens.
3. Produce cytokines and chemokines.
42
What disease is TH1 cells associated with?
Psoriasis
43
What disease is TH2 cells associated with?
Atopic dermatitis
44
What disease is TH17 cells associated with?
Psoriasis and atopic dermatitis
45
Different types of dendritic cell (DC) found in the dermis
1. Dermal
| 2. Plasmacytoid
46
Dermal dendritic cells
Involved in Ag presenting and secreting cyto/chemokines
47
Plasmacytoid dendritic cells
Produce IFNα. Found in diseased skin
48
Neutrophils
Circulating leukocytes attracted to tissue by chemokines (chemoattractant)
49
Mast Cells
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
Class I MHC
o Found on almost all cells
o Present Ag to cytotoxic T cells
o Present endogenous Ag
51
Class II MHC
o Found on APC (B cells, macrophages)
o Present to TH cells
o Present exogenous Ag
52
Secondary (acquired) immunodeficiency diseases
1. AIDS
2. Malignancy
3. Aging
4. Diabetes, renal malfunction, burns, alcoholic cirrhosis, malnutrition
53
Type I (immediate) hypersensitivity (Allergy)
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
Type II hypersensitivity reaction
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
Type III hypersensitivity reactions
An abnormal immune response is mediated by the formation of antigen-antibody aggregates called immune complexes
56
Arthus reaction
A type of local type III hypersensitivity reaction - involve the deposition of antigen/antibody complexes mainly in the vascular walls, serosa, and glomeruli.
57
Type IV hypersensitivity
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
Common local side effects of drugs applied to the skin
```
Superficial skin disorders e.g psoriasis & eczema
Skin infections
Itching
Dry skin
warts
```
59
Pruritis
Itching
60
Glucocorticoids
Possess anti-inflammatory, immunosuppressant and vasoconstricting effects plus anti-proliferating action upon keratinocytes and fibroblasts
61
Skin failure consequences
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
First degree burns
Epidermis only.
63
Second degree burns
Second degree/Partial thickness: epidermis and dermis.
64
Third degree burns
Third degree/ Full thickness: extends beyond dermis.
65
Chronic wounds
(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
Purpura (colour)
Due to extravasation (leakage of fluids from a vein) of blood, will not blanche, may be raised
67
Petechia
Smaller 1-2mm area of purpura
68
Erythema
Due to vascular dilatation, will blanche on pressure
69
Macule
< 1cm flat lesion
70
Patch
> 1cm FLAT lesion
71
Papule
< 0.5cm raised lesion
72
Nodule
> 0.5cm raised lesion
73
Plaque
Raised edge but flatter surface
74
Wheal
Compressible dermal swelling
75
Vesicle
< 0.5cm fluid-filled lesion
76
Bulla
> 0.5cm fluid-filled lesion
77
Cyst
Is a nodule (> 0.5cm raised lesion) containing semi-solid material
78
Pustule
Pus filled
79
Scale
Accumulated fragments of keratin layer
80
Crust
Dried exudate e.g serum
81
Lichenified
Skin thickening with increased skin markings
82
Scar
Normal tissue replaced by fibrous tissue
83
Erosion
Superficial break in epidermis
84
Ulcer
Deeper break in epidermis
85
Fissure
Linear split in epidermis
86
Atrophy
Loss of epidermis +/- dermis but surface remains intact
87
Examples of Type I ( immediate) hypersensitivity reactions
Urticaria
Angio-oedema
Anaphylaxis
88
Examples of Type IV ( immediate) hypersensitivity reactions
Allergic contact dermatitis
Photo-allergy
Skin response to bacteria, fungi, viruses.
89
Patch testing
Useful skin test to identify contact allergens (type IV hypersensitivity)
90
Which two reaction types are most commonly seen in the skin?
Type I and Type IV
91
Systemic side effects of glucocorticoids
1. Suppression of HPA axis
2. Cushing's disease (rare)
3. Growth retardation (extremely rare)
92
The 2 categories for food hypersensitivity
1. Immune mediated (food allergy)
| 2. Non-immune mediated reactions (food intolerance).
93
The 2 categories for food allergy
1. IgE-mediated (immediate onset) '
| 2. Non-IgE mediated (delayed onset).
94
Most common food allergens
```
Cow’s milk
Chicken egg
Fish
Shellfish especially prawns,
Soya
Peanuts
Tree nuts
Wheat
```
95
Prick test
Intradermal injection of suspected substance e.g. latex. Look for wheal and flare reaction within 30mins.
96
Calcineurin Inhibitors
* Tacrolimus, pimecrolimus
| * Suppress lymphocyte activation
97
Antifungal creams
Clotrimazole,
Terbinafine
Ketoconazole
98
Keratolytics
Used to soften keratin e.g salicylic acid
99
Hyperkeratosis
Increased thickness of keratin layer
100
Parakeratosis
Persistence of nuclei in keratin layer
101
Acanthosis
Increased thickness of epithelium
102
Papillomatosis
Irregular epithelial thickening
103
Examples of Type II hypersensitivity reactions
Pemphigus & pemphigoid
104
Examples of Type III hypersensitivity reactions
Purpura/rash
105
Fitzpatrick classification
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
Vitamin D
A fat-soluble pro-hormone essential for calcium and phosphorus metabolism.
107
Actinic lentigines
* Actinic or solar lentigines (singular lentigo)
* Also known as ‘age’ or ‘liver’ spots
* Related to UV exposure
108
Freckles
* Patchy increase in melanin pigmentation
* Occurs after UV exposure
* Most common in fair skinned and red heads
