Session 10: Skin Flashcards
1
Q
Main functions of the skin
A
- Protection/barrier = UV light/pathogens
- Immunity
- Sensation
- Thermoregulation
- Metabolic function = synthesis of vitamin D, storage of subcutaneous fat
- Psychosexual communication
2
Q
Normal human scalp skin (H&E)
A
3
Q
Layers of epidermis (deep to superficial)
A
- stratum basale = basal layer
- stratum spinosum = spinous layer
- stratum granulosum = granular layer
- stratum lucidum = in thick skin (additional layer)
- stratum corneum = cornified layer
4
Q
In thick skin, an additional layer can be found between the granular (stratum granulosum) and cornified (stratum corneum) layers. This additional layer is called…
A
Stratum lucidum
5
Q
The predominant cell type of the epidermis is the…
A
Keratinocyte
6
Q
The stratum corneum (cornified layer) is much thicker in which regions of the skin?
A
Palmar
Plantar
7
Q
What are the function of these ridge structures (dermal papillae) which the arrow is pointing to in this image of a normal finger epidermis (H&E)?
A
Increase the surface area for the attachment of the epidermis
They influence shape of the cornified layer - forming fingerprints
8
Q
Spinous cells in the stratum spinosum of the epidermis are joined by what intercellular junctions?
A
Desmosomes
9
Q
Basal keratinocytes undergo cell division to form ___ amplifying cells
A
transit amplifying cells
10
Q
The transit time of a keratinocyte from the basal layer (deepest) to being sloughed off from stratum corneum (superficial) is approximately ___ days
A
28 days
11
Q
The stratum granulosum (granular layer) is characterised by ___ granules
A
Keratohyalin
12
Q
What do keratohyalin granules contain
A
1) Intermediate filaments = K1, K10
2) Enzymes (phospholipases, transglutaminases)
3) Filaggrin = filament aggregating protein
4) Involucrin = forms major part of cornified envelope
13
Q
The stratum corneum (cornified layer) is made up of layers of flattened, anucleate ___ embedded in a waxy lipid ‘cement’ (containing ceramides, cholesterol, squalene)
A
corneocytes
14
Q
Corneocytes
A
Role in skin barrier function
Another name for a stratum corneum cell. Hardened, waterproof, protective keratinocytes; these ‘dead’ protein cells are dried out and lack nuclei.
15
Q
Ultimately, corneo-desmosomes break down and ___ are ‘sloughed off’ as scales of skin
A
corneocytes
16
Q
The cornified layer ___ with skin abrasion. This is why the soles of feet/hands are thicker than e.g., eyelid skin
A
thickens
17
Q
Difference between thick and thin skin
A
stratum lucidum
18
Q
Actinic (solar) keratosis
A
Premalignant lesions state
* Epidermal dysplasia
* 8-20% may progress to squamous cell carcinoma (SCC)
* Scaly plaque texture
* Due to chronic sun exposure
19
Q
Chronic sun exposure can lead to epidermal dysplasia in the form of ___ ___ (AK)
A
Actinic keratosis (AK)
20
Q
___% of actinic (solar) keratosis may progress to ___ cell carcinoma
A
8-20% of actinic (solar) keratosis may progress to squamous cell carcinoma
21
Q
Non-melanoma skin cancers
A
- Squamous cell carcinoma (SCC)
- Basal cell carcinoma (BCC)
22
Q
Basal cell carcinoma (BCC) originates in the…
A
Follicular keratinocytes
23
Q
Basal cell carcinoma carries a ___ risk of metastasis
A
low risk of metastasis (~0.05%)
24
Q
Squamous cell carcinoma (SCC) originates in the…
A
Basal keratinocytes
25
Squamous cell carcinoma (SCC) can arise in pre-existing regions of ___ ___
Actinic keratosis (AK)
26
Squamous cell carcinoma (SCC) carries a ___ risk of metastasis
higher risk of metastasis (0.5-3%)
27
Squamous cell carcinoma (SCC) accounts for ___% of non-melanoma skin cancers (NMSCs)
Squamous cell carcinoma (SCC) accounts for 20% of non-melanoma skin cancers (NMSCs)
28
Histological features of squamous cell carcinoma (SCC)
- Palisading keratinocytes pushing down into dermis
- Keratin pearls
- Immune cell infiltration
29
What is Psoriasis
Chronic autoimmune inflammatory disease
30
What is psoriasis associated with
- Extreme proliferation of the epidermal basal layer (stratum basale) in response to inflammatory cytokines
- Epidermal turn-over reduced to 3-7 days from normal 28 days
31
Approximately ___% of the world population suffers from psoriasis
2%
32
___ psoriasis accounts for 90% of all psoriasis cases
Plaque psoriasis
33
Management of the symptoms of psoriasis
- Phototherapy = sunlight
- Vitamin D analogues = promote differentiation
- Topical steroids = suppress inflammation
- Anti-inflammatory medication = Apremilast
34
Psoriasis can be ___ or widespread
localized
35
Psoriasis leads to profound effects on the skin barrier function - these effects include...
- Dry skin = loss of fluid
- Increased sensitivity = to exogenous agents
- Compromised thermoregulation
36
Other cells found in the epidermis
- Melanocytes = stratum basale
- Langerhans cells = dendritic APCs of immune system in stratum spinosum
- Merkel cells = mechanoreceptors in stratum basale
37
What type of cells are melanocytes?
Dendritic cells
## Footnote
Secrete melanin pigment
38
Function of melanocytes
Produce melanin
39
Where are melanocytes found?
Stratum basale (basal layer)
40
What is the name of the organelles found in melanocytes that produce melanin
Melanosomes
41
Benign lesions in sun-exposed sites of skin
Freckles (due to temporary over-production of melanin)
42
Lesions that arise in middle age and result from an increase in melanocytes
Solar (or actinic) lentigines
43
Solar or actinic lentigines has a risk of progressing to ___ ___ melanoma
Lentigo maligna melanoma
44
Sunburn is a response to UV over-exposure. This is characterised by three signs...
1) Keratinocyte apoptosis
2) Erythema
3) Oedema
45
Long-term sun exposure is associated with what three conditions?
1) Actinic keratoses
2) Squamous cell carcinoma (SCC)
3) Basal cell carcinoma (BCC)
46
Loss of pigmentation
Vitiligo
47
Vitiligo caused by...
Autoimmune destruction of melanocytes - producing symmetrical, localized areas of depigmentation on skin
48
Malignant melanoma
Most aggressive form of skin cancer; often characterized by black or dark brown patches on the skin that may appear uneven in texture, jagged, or raised.
49
In malignant melanoma...
Retention of tumour cells ABOVE the basement membrane is associated with a ___ prognosis - this is also known as superficial spreading melanoma
Breslow depth < 1mm
5-year survival = 95-100%
50
In malignant melanoma...
More penetrating nodular melanomas may have a very ___ prognosis
Breslow depth > 4mm
5-year survival = <50%
51
Benign growths of melanocytes
Common moles
52
Malignant melanoma warning signs (ABCDEFG method)
A) Asymmetry
B) Border
C) Colour
D) Diameter
E) Elevation
F) Firm
G) Growing
53
Malignant melanoma histology
1. Melanocytes that grow into the dermis
2. Most lethal via metastasis
54
What are Merkel cells, where are they located?
Mechanoreceptors for light touch detection
They are found in the stratum basale (basal layer) of epidermis
55
Merkel cell carcinoma (MCC)
A relatively rare but potentially aggressive and difficult-to-treat cancer
56
Causes of Merkel cell carcinoma (MCC) aetiology
- Viral
- UV-mediated
57
Sebaceous glands (SB) in the face of an adult (H&E)
H&E staining
58
List some skin appendages
- Eccrine sweat gland
- Sebaceous gland
- Apocrine sweat gland
- Hair shaft
59
Eccrine sweat glands (H&E)
60
Sebaceous duct in sebaceous gland (H&E)
61
Acne is a disease of the ...
Sebaceous glands
62
Sebaceous glands can be found abundant on the ___ and ___
Face and chest
## Footnote
(typical sites for acne)
63
The cause of acne is obscure, however, it is highly associated with...
1) Increased sebum production at puberty
2) Colonisation with normally harmless bacteria (Cutibacterium acnes)
3) Abnormal differentiation of sebaceous gland ducts leading to obstruction
64
Acne is associated with the accumulation of harmless skin bacteria such as ...
Cutibacterium acnes
65
Scalp skin (H&E)
66
Alopecia is a condition characterised by...
Autoimmune hair loss
67
Androgenic alopecia caused by...
Genetic sensitivity to the androgen DHT (dihydrotestosterone)
68
Alopecia areata
Patchy loss of hair occurring on the scalp or other parts of the body
69
Alopecia totalis
Total loss of scalp hair
70
Alopecia universalis
The total loss of hair on all parts of the body
71
Alopecia management
- Purchase wigs
- Mild shampoos and avoid all harsh chemicals
- Psych consideration
- Local steroid treatments can be effective
72
What is the 'basement membrane zone' in the skin?
Dermo-epidermal junction
73
Epidermolysis bullosa (EB)
A group of hereditary disorders characterized by inadequate or faulty synthesis of keratin, collagen, and/or basement membrane.
Resulting in lack of cohesion between layers of the skin and mucosa.
Leads to painful blistering.
74
Epidermolysis bullosa simplex (EB simplex)
* A genetic disorder caused by mutations in keratin genes (defects in basal keratins K5/K14)
75
Dystrophic epidermolysis bullosa (DEB)
* Inherited defect in Collagen VII which anchors the basement membrane to underlying tissue
* Leads to shearing of skin, butterfly skin, delicate/fragile skin
76
Treatment of epidermolysis bullosa (EB)
- Management of wounds
- Analgesics (pain management)
- No cure
77
Dermis
Middle layer of skin
78
What two layers make up the dermis
1) Papillary layer
2) Reticular layer
79
What cells can be found in dermis
fibroblasts, adipocytes, immune cells (WBC, macrophages, mast cells)
80
The characteristic 'basket-weave' appearance of the dermis helps its vital function of...
Resisting shearing forces (protection from injury) in multiple planes
81
Is the dermis vascular
Yes, highly vascular and innervated
- Lymphatic vessels
- Nerves
82
Two types of ageing
1) Intrinsic (chronological)
2) Extrinsic (photoageing) = UV-induced injury to collagen & elastin
83
Extrinsic photoageing
UV-induced injury to dermal collagen and elastin
84
How does ageing affect skin?
• Decreased = hair follicles & sweat glands, epidermis thickness, collagen, elastin & subcutaneous fat
• Increased = cross linking of collagen and elastic tissue (which decreases the elasticity of the skin and makes it more fragile)
85
Sun exposed skin texture (photoageing)
Flattening of surface of skin due to loss of normal underlying dermal architecture.
86
Scar tissue resulting from rapid stretching of the dermis. Collagen fibres become orientated along stress lines
Stretch marks (striae)
87
Damage to collagen...
Stretch marks (striae)
88
UV rays penetrate deep into the dermis, where they damage ___ fibers. This damage leads to increased production of abnormal ___
UV rays penetrate deep into the dermis, where they damage collagen fibers. This damage leads to increased production of abnormal elastin
89
Solar elastosis
Excess UV light exposure breaks down the collagen and elastic fibers in the skin
90
Keloid scarring
Excessive fibrosis (excessive scarring) following wounding - tender and painful.
91
Keloid scarring is due to overactivity of what cell?
Fibroblasts
92
___-skinned people are more likely to form keloid scars
Dark
93
A superficial capillary malformation presenting as a pink or red patch
Nevus flammeus (port wine stain)
94
Mast cells can be found in the skin. They are important in innate immunity. They mediate type ___ immediate hypersensitivity allergic reactions.
Mast cells can be found in the skin. They are important in innate immunity. They mediate type one (I) immediate hypersensitivity allergic reactions.
In these reactions, histamine is released causing increased vascular permeability and leakage of plasma into extravascular sites, causing local oedema.
95
Allergic reactions (mast cell degranulation) following exposure to allergen can affect the superficial dermis causing...
Urticaria
96
Allergic reactions (mast cell degranulation) following exposure to allergen can affect deeper tissues causing...
Angioedema
97
What cells are found in the skin and are important in innate immunity?
Mast cells
## Footnote
They mediate type one (I) immediate hypersensitivity allergic reactions.
98
What do allergic reactions (mast cell degranulation) following exposure to allergen affect in the superficial dermis?
Urticaria
99
What do allergic reactions (mast cell degranulation) following exposure to allergen affect in deeper tissues?
Angioedema
## Footnote
This can be serious if the upper respiratory tract becomes inflamed as well.
100
What condition can diabetes lead to?
Peripheral neuropathy
101
What type of neuropathy is associated with diabetes?
Peripheral neuropathy
102
What does leprosy (Hansen's Disease) cause?
Inflammation and damage to nerves in the skin (cutaneous innervation damage)
103
What mechanoreceptors in the skin are sensitive to pressure and vibration?
- Pacinian corpuscle
- Lamellar corpuscle
104
What mechanoreceptors in the skin are sensitive to light touch?
- Meissner's or tactile corpuscle
105
What process is essential for maintenance of body temperature?
Vascular thermoregulation
106
What occurs during vascular thermoregulation?
1) Dilatation of skin blood vessels → heat loss
2) Constriction of skin blood vessels → heat conservation
107
What does dilatation of skin blood vessels lead to?
Heat loss
108
What does constriction of skin blood vessels lead to?
Heat conservation and pallor
109
What is the result of failure of widespread vascular thermoregulation?
Erythrodermic psoriasis
110
What is the result of failure of extremity vascular thermoregulation?
Raynaud's phenomenon
111
Name two disorders caused by a failure of vascular thermoregulation.
1) Widespread = Erythrodermic psoriasis
2) Localised = Raynaud's phenomenon
112
What three conditions are associated with long term sun exposure?
1) Actinic keratoses (AK)
2) Squamous cell carcinoma (SCC)
3) Basal cell carcinoma (BCC)
113
Why is it not advisable to excise a keloid scar?
Excess collagen deposition during repair will exacerbate the scar
114
What type of alopecia is characterized by irreversible hair loss due to permanent damage to follicular stem cells?
Scarring alopecia
115
What type of alopecia is characterized by loss of patches of scalp hair?
Alopecia areata
116
What type of alopecia is characterized by loss of all body hair?
Alopecia universalis
117
What type of alopecia is characterized by complete loss of scalp hair?
Alopecia totalis
118
What is the embryonal origin of melanocytes?
Neural crest
119
What disorder is characterized by salty sweat arising from inability to reabsorb extracellular sodium due to CFTR mutation?
Cystic fibrosis
120
What disorder is characterized by autoimmune destruction of melanocytes?
Vitiligo
121
What disorder is characterized by blistering resulting from collagen VII mutations?
Epidermolysis bullosa
122
What disorder is characterized by a pre-malignant thickening of the epidermis?
Actinic keratosis
123
What disorder is characterized by excessive scarring resulting from overactive collagen deposition by fibroblasts?
Keloids
124
What disorder is characterized by deep tissue swelling arising from hypersensitivity reaction mediated by mast cells?
Angio-oedema
125
What does psoriasis lead to in terms of epidermal layer thickness?
Psoriasis leads to increase in thickness of the spinous layer.
## Footnote
A poorly formed granular layer means that formation of the stratum corneum is compromised, leading to the formation of plaques.
126
In which layer of the epidermis would you find keratohyalin granules?
Stratum granulosum, stratum spinosum
127
What molecules do keratohyalin granules contain?
- Involucrin
- Transglutaminases to cross-link proteins
- Filaggrin
- Keratins
128
What is the function of epidermal Langerhans cells?
They are antigen presenting cells
129
In a case study of a skin rash/lesion, what layers of the epidermis are identified?
A = Stratum corneum
B = Stratum granulosum
C = Stratum spinosum
D = Stratum basale
130
Where is the stratum lucidum found in the epidermis?
Between the granular layer and the cornified layer
131
On which layer of the epidermis do inflammatory cytokines act to promote hyperproliferation?
Stratum basale
132
What external surface of the body has an epithelium that is not protected by a stratified squamous keratinised epithelium?
Cornea
133
What disorder is characterized by the destruction of melanocytes?
Vitiligo
134
Compare the two main forms of non-melanoma skin cancers - squamous cell carcinoma (SCC) and basal cell carcinoma (BCC).
135
What layer of the epidermis can melanocytes be found?
Stratum basale
## Footnote
Cells that produce melanin from melanosome organelles.
136
What layer of the epidermis can Langerhans' cells be found?
Stratum spinosum
## Footnote
Dendritic APC immune cells.
137
What layer of the epidermis can Merkel cells be found?
Stratum basale
## Footnote
Mechanoreceptors associated with somatosensory nerve endings.
138
What is dysplasia?
Abnormal development or growth of cells, tissues, or organs
## Footnote
May signify a stage preceding the development of cancer.
