Skin Flashcards
Give a definition for ‘skin’ including its functions (4)
The skin is a self-repairing barrier.
It permits terrestrial life by preventing the entering of microorganisms and chemicals whilst regulating heat and water loss from the body.
What is the integumentary system?
The organ system that protects the body from various kinds of damage, such as loss of water or abrasion from outside.
The system comprises the skin and its appendages (including hair, scales, feathers, hooves, sweat glands and nails).
Where would the stratum corneum mostly be located on the body? What is its function?
On load bearing areas of the body e.g. the palms of your hands and soles of your feet
It provides mechanical support and a rigid barrier (so when you stop on something, it does not go straight into the body)
What is transdermal delivery? Give 4 advantages of transdermal delivery
Transdermal delivery is defined as getting across the skin for systemic action
Advantages include:
1. large surface area so potentially numerous sites
- Good patient compliance (e.g. it’s discrete)
- Easy cessation of therapy in problematic cases
- Avoidance of first pass hepatic metabolism (and therefore no systemic side-effects)
What’s the most common way in which drugs permeate through the skin? (2)
Through the follicles and sweat ducts (shunt route)
What are appendages in terms of drug delivery and skin?
The appendages are essentially shunt routes (short-cuts) through which molecules can pass across the stratum corneum barrier
Name 3 appendages found that originate in the dermis
- Hair follicles and associated sebaceous glands
- Eccrine (sweat) glands
- Apocrine (specialised e.g. milk - nipples) glands
What are the 2 micro routes for permeation via the stratum corneum?
- transcellular (across the cell)
2. intercellular (between lipids)
Name 3 potential routes through intact skin
- Shunts (holes)
- Intercellular (between lipids)
- Transcellular (across the cell)
Out of shunts, intercellular and transcellular, which one is the major route through intact skin to reach the systemic circulation?
Intercellular route (between lipids)
Define permeant
the molecule moving into or through the skin
What does Flick’s Law of Diffusion assume?
The law assumes that diffusion is through an isotropic (meaning same properties in all dimensions) material (aka skin).
What is a Franz cell used for?
A Franz diffusion cell is used to measure the delivery of a drug through skin
What is the main drive for drug delivery?
Thermodynamic activity
What are key characteristics in selecting a good molecule candidate for skin? Hint MW, LogP, Aqueous solubility
- MW 300-500
- LogP 1 - 3.5
- Aqueous solubility > 100 mg/ml
Give the rationale for topical delivery (4)
- low oral bioavailability
- Short half-life
- Potential to induce insulin resistance at high doses in diabetic patients
- long-term treatment
What is basal cell carcinoma (rodent ulcer)?
Basal cell carcinoma is a type of skin cancer.
It’s the least malignant and most common form of skin cancer.
It’s common in later life. Lesions are often on sun-exposed areas of the face.
Lesions appear shiny, dome-shaped nodules that later develop during central ulcer with pearly, beaded edge
It’s relatively slow-growing and metastasis seldom occurs before detection
What’s the treatment for basal cell carcinoma (rodent ulcer)?
Treatment:
- full cure by surgical excision
- radiotherapy useful in large superficial forms
- cryo-therapy can be used for superficial forms
What is squamous cell carcinoma?
Squamous cell carcinoma arises from keratinocytes of stratified squamous epithelium.
lesions are scaly red papules that can ulcerate and bleed
found on head (scalp, ears, lower lips) and hands
grows rapidly and metastases if not removed
What is malignant melanoma?
It is the most dangerous of all skin cancers.
Exposure to UV radiation is a major cause
It’s common on head, face, hands, back (men) and lower left (women).
It’s highly metastatic and resistant to chemotherapy
it occurs spontaneously in melanocytes and can begin wherever there is a pigment
What advice would you to people in regards to the dangers of sunbathing?
- avoid sun exposure during hours 11am-3pm
- wear a sun hat
- apply high protection sunscreen e.g. SPF30 and re-apply at regular intervals
What is the USA criteria for recognising melanoma?
ABCD(E)
A: Asymmetry - one half doesn’t match the appearance of the other half
B: Border irregularity - the edges are ragged, notched, or blurred
C. Colour - the colour (pigmentation) is not uniform. Shades of tan, brown and black are present. Dashes of red, white and blue add to a mottled appearance
D: Diameter - the size of the mole is great than 1/4 inch (6mm).
E: Elevation - any growth of a mole should be evaluated
Describe the 7-point checklist for melanoma (UK criteria)
Major criteria:
- change in size
- change in shape
- change in colour
Minor criteria: - diameter > 6mm - inflammation - oozing/bleeding mild itch or altered sensation
What type of infection is candidiasis?
Candidiasis are fungal infections (meaning thrush)
Where on the body does tinea capitis occur? At what age is it usually seen in and how is it spread?
the scalp. Usually seen in children and is spread by close-contact (especially in schools and households)
Where on the body does tinea corporis occur? Name some of its symptoms
the body (truck and/or limbs).
Symptoms include isolated erythematous and scaly lesions or clusters of round or oval red patches
Where on the body does tinea cruris occur? Where is it more common in? What are some of the symptoms?
Groin.
It’s common in warmer climates and involves itching in the groin thigh skin folds or anus. it’s red, raised, scaly patches that may blister and ooze.
Where on the body does tinea pedis occur?
feet (also known as athletes foot). It appears in toe clefts
It presents as red, scaly eruption that itches.
What is tinea?
Tinea is used to describe skin mycoses. It’s sometimes called ‘ringworm’
What is onchomycosis?
It’s a nail infection
What is the treatment for localised ringworms?
Imidazoles (e.g. clotrimazole, miconazole) or terbinafine
Apply 3 times daily for 1-2 weeks
What is the treatment for Athletes foot?
Terbinafine 1% cream or spray
What’s the treatment for widespread tinea infections?
Adults: Oral antifungal -Terbinafine (250mg OD) or Itraconazole (100mg OD) for 1-2 months
Children: Griseofulvin
What is the role of NMF (natural moisturising factors)? (5)
- flexibility
- cohesion
- hydration
- plays as a buffer (as pH increases, NMF decreases)
- integrity
What happens when there is a loss of filaggrin?
A loss of filaggrin results in:
- corneocyte deformation (meaning flattening of the surface skin cells)
- a reduction in NMF
- an increase in skin pH which encourages serine protease activity (the enzymes which digests lipid-processing enzymes and desmosomes in addition to promoting skin inflammation)
What are the symptoms of atopic eczema (dermatitis)? (4)
- Dry
- Scaly
- Erythematous
- Itchy rash (particularly noticeable on face, scalp, neck inside elbows and behind knees)
N.B. If often resides in childhood but can continue into adulthood
What are the 3 possible triggers for eczema (Dermatitis)?
- Internal inflammation
- Eternally applied chemicals e.g. soaps
- Environment e.g. humidity
How does irritant contact eczema usually occur?
It results from damage to skin from topically applied liquids or chemicals in absence of an allergic mechanism
How does allergic contact eczema occur?
Patients are allergic to a specific allergen. Whenever skin comes into contact with that allergen, then a eczematous rash occurs e.g. from nickel (jewellery, studs), leather, dyes, plans etc.