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Tissues of the Body > Lecture 8.2: Skin > Flashcards

Lecture 8.2: Skin Flashcards

1
Q

Main Functions of the Skin (5)

A

• Protection/Barrier function/Immunity
• Sensation
• Thermoregulation
• Metabolic Functions (Vitamin D Synthesis & Storage of Subcutaneous Fat)
• Psychosexual communication

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2
Q

The Layers of the Epidermis: Outwards to Inwards

A

• Cornified layer (stratum corneum)
• Granular layer (stratum granulosum)
• Spinous layer (prickle cell layer or stratum spinosum)
• Keratinocytes maturing and synthesizing keratin
• Basal layer (stratum basale)

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3
Q

What is Adermatoglyphia?

A

No fingerprints
Caused by mutation in SMARCAD1

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4
Q

Granular Layer: the Last Living Layer

A

This layer is characterised by keratohyalin granules containing:

• Intermediate filaments (K1 and K10)
• Enzymes that degrade the phospholipid bilayer (phospholipases) and cross-link
proteins (transglutaminases)
• Filaggrin, which aggregates keratins (mutations associated with severe
dermatitis and scaling disorders)
• Involucrin, which forms a major part of the cornified envelope

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5
Q

The Cornified Layer

A

Made up of layers of flattened, anucleate corneocytes embedded in a waxy lipid “cement” (containing ceramides, cholesterol, squalene)

Ultimately, corneo-desmosomes break down and corneocytes are ‘sloughed off’ as squames (scales)

The cornified layer thickens with skin abrasion

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6
Q

Disorders of Keratinocytes: Actinic (Solar) Keratosis

A

Chronic sun exposure can lead to epidermal dysplasia in the form of actinic keratosis (AK)

This is a pre-malignant state, and 8-20% may progress to squamous cell carcinoma (SCC)

Scaly Plaque typical of AK

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7
Q

Non-Melanoma Skin Cancers: Squamous Cell Carcinoma

A

Originates in basal keratinocytes and can arise in pre-existing regions of AK

SCC carries a higher risk of metastasis compared to BCC

It accounts for ~20% of NMSCs

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8
Q

Non-Melanoma Skin Cancers: Basal Cell Carcinoma

A

Basal Cell Carcinoma (BCC; rodent ulcer) accounts for >75% of NMSCs

This disease is thought to originate in follicular keratinocytes

It carries a low risk of metastasis (~0.05%)

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9
Q

Psoriasis

A

It is an autoimmune and inflammatory disease, known to have both a genetic component and environmental triggers

Associated with extreme proliferation of the epidermal basal layer in response to inflammatory cytokines

Epidermal turn-over is reduced to 3- 7 days (from 28 days)

Reduction of granular layer leads to a disrupted cornified layer

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10
Q

Plaque Psoriasis: where does it affect?

A

Plaque psoriasis (90% of cases) typically affects elbows, knees, scalp and back, but any area of the skin (including nails) can be involved

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11
Q

Plaque Psoriasis: Treatments

A

• Symptoms can improve with sunlight (phototherapy)
• Vitamin D analogues (to promote differentiation)
• Topical steroids (to suppress inflammation)
• Newer treatments include the anti-inflammatory drug apremilast

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12
Q

Melanocytes

A

Are associated with the Basal Layer of the epidermis

Dendritic cells of neural crest origin

Contain organelles called ‘melanosomes’ that produce melanin

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13
Q

Melanosomes

A

Organelles found in melanocytes that produce melanin

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14
Q

Langerhans’ Cells

A

Are dendritic antigen presenting cells of the immune system

They form a sentinel network in the spinous layer (prickle-cell layer)

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15
Q

Merkel Cells

A

Are touch receptors located in the basal layer

These are mechanoreceptors for light touch detection located in basal layer of the epidermis

Associated with somatosensory nerve endings

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16
Q

Sun Exposure

A

Freckles are common benign lesions in sun-exposed sites

UV exposure stimulates a temporary over-production of melanin

Solar (or actinic) lentigines arise in middle age (liver spots) resulting from an increase in melanocytes, thus do no fade

Risk of progression to lentigo maligna melanoma

17
Q

Sunburn

A

A response to UVB over-exposure, characterised by:
• keratinocyte apoptosis,
• erythema (reddening)
• oedema

Associated with actinic keratoses, and both squamous cell carcinoma
and basal cell carcinoma

18
Q

Skin type catagorisation

A

Type I to VI
Lightest to Darkest

19
Q

Actinic Keratoses

A

Dry scaly patches of skin that have been damaged by the sun

20
Q

Vitiligo

A

Autoimmune disease in which the immune system attacks melanocytes, this results in loss of pigmentation in symmetrical, well-demarcated, localised areas of skin

21
Q

Malignant Melanoma

A

An aggressive malignant tumour of melanocytes

Retention of tumour cells above the basement membrane is associated with a
good prognosis

22
Q

Malignant Melanoma Incidence and ABCDE(FG) Warning Signs

A

Asymmetry
Border
Colour
Diameter
Elevation
Firm
Growing

23
Q

Merkel Cell Carcinoma (MCC)

A

Is a very rare, but aggressive and difficult-to-treat cancer

MCC can have a viral or UV-mediated aetiology

24
Q

Skin Appendages

A

• Eccrine Sweat Gland
• Sebaceous Gland
• Arrector Pili Muscle
• Apocrine Sweat Gland
• Hair Follicle (forms pilosebaceous unit with the sebaceous gland)
• Infundibulum

25
Q

Androgenic Alopecia

A

Caused by hair follicle miniaturisation in response to dihydrotestosterone exposure

Local steroid treatment may be effective for some

Scarring alopecias are caused by irreversible damage to follicular stem cells

26
Q

Autoimmune Hair Loss: Alopecia Areata

A

Hair begins to fall out, often in clumps the size and shape of a quarter

The extent of the hair loss varies; in some cases, it is only in a few spots

27
Q

Autoimmune Hair Loss: Alopecia Totalis

A

Total scalp hair loss

28
Q

Autoimmune Hair Loss: Alopecia Universalis

A

Loss of all body hair

29
Q

Acne

A

A disease of sebaceous glands

Acne is associated with:
• Increased sebum production at puberty
• Colonisation with normally harmless skin bacteria (e.g. Cutibacterium acnes)
• Abnormal differentiation of sebaceous gland ducts leading to obstruction

30
Q

How much sweat does a normal adult produce daily?

A

1 litre

31
Q

Apocrine Sweat Glands

A

These are large sweat glands that are most abundant in axillae, genital and sub-mammary areas

They produce an odourless, protein-rich, merocrine secretion

Digestion of proteins by cutaneous microbes produces body odour

32
Q

Epidermolysis Bullosa (EB)

A

Mechanically-fragile skin arising from mutations in a range of structural proteins, leads to blistering

Defects in basal keratins K5/K14 (EB simplex)

Defects in collagen VII anchoring fibrils cause dystrophic EB

33
Q

Epidermolysis Bullosa (EB): Treatments

A

Treatment involves management of wounds and pain (no cure)

34
Q

The Dermis

A

The dermis gives the skin mechanical resilience, and is comprised of structural
proteins and a variety of cell types (fibroblasts, adipocytes, immune cells)

Its characteristic “basketweave” appearance resists shear in multiple planes

It is highly vascular, and contains nerves and lymphatic vessels

35
Q

Skin Ageing: Intrinsic (Chronological)

A
36
Q

Skin Ageing: Extrinsic (Photoageing)

A

Tissues of the Body (18 decks)

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