Dermatology Science Flashcards by Jonas Repkewitz

What is the embryological origin of the epidermis?

Ectoderm

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What is the embryological origin of dermis?

Mesoderm

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In week 14 of development the skin consists of?

Basal layer, intermediate layer, periderm (apotheoses 120 days post-fertilisation)

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When do melanocytes, sebaceous glands, arrestor pili muscles and hair follicles develop?

Week 26

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How do melanocytes form?

Melanoblast from neural crest migrates to uveal tract and leptomeninges
Settle in skin

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What are the 5 layers of the epidermis?

Stratum basale
Straum spinosum
Stratum granulosum
Stratum lucidum
Stratum corneum

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Keratinocytes in the basal layer of epidermis attach to basement membrane via?

Hemidesmosomes

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The epidermis is normally regenerated every?

28 days

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How do melanocytes function in the skin?

Melanosomes convert tyrosine into melanin pigment with absorbs light
DCs transport melanosomes to adjacent keratinocytes and form protective melanin cap over nucleus to protect basal cell DNA

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What colour is eumelanin?

Brown/black

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What colour is phaeomelanin?

Red/yellow

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What determines pigment balance in the skin?

MC1R gene. Protein converts eumelanin to phaeomelanin

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1 defective copy of MC1R results in?

Freckling

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2 defective copies of MC1R results in?

Freckling + Red hair

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What are Merkel cells?

Pressure receptors

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What is contained within basal layer?

Keratinocytes
Melanocytes
Merkel cells
Keratin (lots)

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In the prickle cell layer keratinocytes are connected by?

Desmosomes

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Keratinocytes in stratum spinosum produce lamellar bodies. What is their function?

Skin barrier

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What are Langerhans cells and where are they found?

Found in stratum spinosum, dermis and lymph nodes

Mesenchymal immune cells (APCs) - present Ag to T-cells

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What makes up the stratum granulosum?

2-3 layers of flatter unclear keratinocytes

Large keratohyaline granules with filaggrin + involucrin (proteins)

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Which skin layer is the origin of the cornified envelope?

Stratum granulosum

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What do the keratinocytes in the stratum granulosum produce? Function?

Lamellar (aka Odland bodies)

Lipid barrier

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What is the stratum lucid?

Clear translucent layer found only in palms and soles

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The stratum corner serves as a ?

Tight waterproof barrier

Insoluble cornified envelope

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The stratum corner consists of?

Corneocytes (corneodesmosomes) 80% keratin and filaggrin Lamellar granules (release lipids)

What makes up the epidermal basement membrane?

Laminin | Collagen IV

What is the function of the derma-epidermal junction (DEJ)?

Messenging - support, anchor, adhesion, growth and differentiation of basal cells

The DEJ is a _______ membrane

semi-permeable

What makes up the dermis?

``` Ground substance (polysaccharide mix), immune cells Matrix of collagen and elastin Muscles Blood vessels Lymphatics Nerves ```

How is blood supplied to dermis?

Horizontal plexuses (supply > need)

Outline the nerve supply to skin (dermis)?

Somatosensory dermatomes - pacinian (pressure) and meissner (vibration) receptors ANS - bood vessels, nerves, glands

What is the papillary dermis?

Thin dermis found just beneath epidermis

What does the reticular dermis contain?

Hair follicles Nails Skin glands

What do hair follicles consist of?

Pilosebaceous unit | Invaginated epidermal tissue; each associated with dermal sebaceous gland

What makes hair stand up?

Arrector pili muscle

How does the arrector pili muscle attach?

Proximal - hair bulb | Distal - epidermis

How are hair follicles pigmented?

Via above melanocytes

Growth of hair is under _____ influence

hormonal (thyroxine, androgens)

90% of hair is in the growing phase known as?

Anagen

10% of hair is involuted. Known as?

Catagen

How is hair involuted?

Dermal papilla sinks and shrink - hair is pushed back to surface

<1% of hair (50-100/day) is in the asynchronous shedding phase known as?

Telogen

What is hair in utero called?

Lanugo

What is hair in childhood called?

Vellus

What is adult hair called?

Terminal

What makes up a nail?

Specialised keratins in matrix subdivisions (dorsal, intermediated, and ventral plate)

How much does a nail grow in a day?

0.1 mm Fingers > toes Summer > winter

Crumbling in parts of an otherwise normal nail indicates?

Damage to matrix subdivision preventing proper differentiation

What are sebaceous glands?

Produce sebum (small oily layer) to cionrol moisture and protect from fungus/bacteria

Where are sebaceous glands found most and what influences their secretion?

Most on face/chest | Sensitive to hormones - inactive before puberty

What are apocrine glands?

Secrete oily fluid - odour and are part of pilosebaceous unit Unknown function Found mostly in axillae and perineum

What are eccrine glands?

Sweat glands - control moistening and grip on soles. NaCl and HCO3 are reabsorbed

Where are eccrine glands found?

Whole skin (2-4 million) - can produce >10L a day

Under what control are sweat glands?

Sympathetic cholinergic nerve supply | Stimulated by mental/thermal/gustatory

What are the three layers of skin?

Epidermis Dermis Sub-cutis (fat)

What is hyperkeratosis?

Thickened surface keratin layer

What is parakeratosis?

High epidermal turnover - immature keratin, nuclei persist

What is acanthuses?

Increased epithelial thickness

What is papillomatosis?

Irregular epithelial thickening (bumpy)

What is spongiosis?

Oedema filled vesicles

What are the functions of skin?

``` Barrier Metabolism and detox Thermoregulation Immune defence Communication (appearance, odour) Sensory ```

Outline vitamin D metabolism in the skin?

Cholecalciferol is concerted to Vitamin D3 (290-320 mm UV light) Stored in liver with dietary vitamin D Converted to calcitriol in kidney

What percentage of T4 to T3 conversion occurs in the skin?

(0%

how do keratinocytes in the epidermis contribute to immune defence?

Cell surface receptors sense pathogens and produce AMPs, cytokines and chemokine in response

The skin contains mesenchymal T-cells including CD4+, CD8+, NK cells and other subsets. How to TH1 cells activate macrophages?

via IL-2 and IFN-y

The skin contains mesenchymal T-cells including CD4+, CD8+, NK cells and other subsets. How do TH2 cells help B cells make antibodies?

Via IL-4, 5 and 6

Plasmocytoid dendritic cells produce which marker of diseased skin?

IFN-a

What occurs in the sensitisation phase of type IV hypersensitivity?

Haptens presented to CTLs and down-regulatory DC4+ T cells in lymph nodes

What occurs in the efferent phase of type IV hypersensitivity?

Same happens as in sensitisation phase activate CTLs causing cytokines and chemokine to recruit leukocytes

Group A strep causes which kinds of infections?

Throat, severe skin infections

How are GAS organisms classified?

Lancefield (M - emm protein) antigen

What are the major serotypes of GAS?

M1, M3

Which serotypes of GAS cause severe invasive disease?

M3, M18

Which GAS serotype causes epidemics?

emm89

Which virulence factos do GAS possess?

Superantigen toxins | Haemolysins - tissue damage and ulcer

Which adhesions and evasins do GAS possess?

Adhesins for oro-/naso-pharynx | Hyaluronic acid capsule to evade phagocytosis

Which organisms causes neonatal meningitis?

Group B Strep

Which classification do Enterococcus fall under?

y-haemolytic Strep

E. faecalis and E. faecium are bowel ______ that may cause?

commensals | UTIs

Staph aureus causes which kinds of infectioN?

Skin, wound, bone, joint

Which toxins may S. aureus possess?

Enterotoxin SSSST PVL SUperantigen TSST-1

Most strains of CA-MRSA contain which S. aureus released toxin?

PVL

How do super antigens activate more T-cells?

Non-Specific activation - don't require specific antigen

What is the standard treatment for Staph aureus unless it's MRSA?

Flucloxacillin

S. saprophytic causes?

UTIs in women of child-bearing age

Which competitive bacterial flora are found in the skin?

S. epidermidis Corneybacterium Proprionobacterium (acne)

What is a gel?

semisolid with HMW polymers

What is a cream?

Semisolid emulsion of oil in water with emulsifier and preservative

What is an ointment?

Semisolid grease without preservatives

What is a paste?

Semisolid with fine powdered material

What is lotion?

Solution of meds in water

How do you calculate the rate of absorption (J) of topical drugs?

Kp (permeability coefficient) x Cv (concentration of drug in vehicle)

How potent is hydrocortisone 1%?

Mild

How potent is mometasone/betamethasone/valerate 0.1%?

Potent

How potent is clobetasol/proprionate 0.05%

Very potent

How potent are modrasone, clobetasone and butyrate 0.05%

Moderate

Which anti-septic can be used as a rinse-bath for acute exudative eczema, popholyx?

Potassium permangenate

How can topic drugs be systemically absorbed?

Transdermal - LMW | Enhanced by iontophoresis/electroporation

What is the advantage of TDD (transdermal drug delivery)?

Avoids first pass metabolism

Subcutaneous admin is just for ___ molecular weight drugs

high

What are the advantages of subcutaneous administratioN?

Avoids first-pass metabolism | Can introduce depot

How do different skin surfaces rank in permeability

nail << palm/sole < trunk/extremities < face/scalp < scrotum

What is the DLQI?

Dermatology life quality index

Dermatology Science Flashcards

(103 cards)