Skin Function & Acne Vulgaris Flashcards
Describe the embryology of the skin under the following headings:
- where is the epidermis derived from? [1]
- what happens by 5th week? [1]
- what happens by 7th week? [2]
- what happens by 4th month? [1]
- what happens during the early fetal period? [1]
- how and when does hair develop? [2]
- how do sebaceous glands develop? [1]
- how do sweat glands develop? [1]
- Epidermis is derived from:
- the ectoderm
- 5th week:
- the skin of the embryo is covered by simple cuboidal epithelium
- 7th week:
- single squamous layer (called the periderm), and a basal layer forms
- 4th month:
- an intermediate layer, containing several cell layers, is interposed between the basal cells and periderm
- Early fetal period:
- the epidermis invaded by melanoblasts (cells of the neural crest origin)
- Hair:
- develops at 3rd month as an epidermal proliferation into dermis.
- Sebaceous Glands:
- cells of the epithelial root sheath proliferate to form a sebaceous gland bud
- Sweat glands:
- develop as downgrowths of epithelial cords into dermis
Describe the anatomy of the skin
Describe the functions of the skin [3]
-
Protection - primary function as a barrier (physical and immunological)
- Mechanical impacts
- Protects and detects pressure
- Detects variations in extreme temperature
- Barrier to micro-organisms
- Barrier to radiation/chemicals
-
Physiological Regulation
- Body temperature via sweat, hair and changes in peripheral circulation
- Fluid balance via sweat and insensible loss
- Synthesis of Vitamin D
-
Sensation
- Network of nerve cells that detect and relay changes in the environment (heat, cold, touch, and pain)
Name and describe the different types of receptors/nerve endings associated with skin sensation [5]
-
Merkel cells:
- at the base of the epidermis,
- respond to sustained gentle and localised pressure,
- assess shape ledge
-
Meissner corpuscles:
- situated immediately below epidermis
- particularly well represented on the palmar surfaces of the fingers and lips
- especially sensitive to light touch
-
Ruffini’s corpuscles:
- situated in the dermis
- they are receptors sensitive to deep pressure and stretching
-
Pacinian corpuscles:
- mechanoreceptors
- present in the deep dermis,
- sensitive to deep touch, rapid deformation of skin surface and around joints for position/proprioception
-
Other free nerve endings:
- pain
- temperature
What are the 2 components of the skin’s immune system and describe their functions [12]
-
Langerhans cells (LC):
- members of the dendritic cells family, residing in the basal layers
- Specialize in antigen presentation:
- acquire antigens in peripheral tissues,
- transport them to regional lymph nodes,
- present to naive T cells
- initiate adaptive immune response
-
Activated T cells:
- initiate cytokine release cascade
- involved in:
- antimicrobial immunity,
- skin immunosurveillance,
- induction hypersensitivity
- pathogenesis of chronic inflammatory diseases of the skin
Define skin allergy and describe its pathophysiology [4]
- Skin irritation by nonallergenic and allergenic compounds induces Langerhans cell migration and maturation
- Langerhans cells migrate from epidermis to draining lymph nodes
- Initial sensitization takes 10-14 days from initial exposure to allergen (nickel, dye, rubber etc.)
- Once an individual is sensitized to a chemical, allergic contact dermatitis can then develop within hours of repeat exposure
Describe the direct damaging effects of UV light on the skin [7]
- Direct cellular damage & alterations in immunologic function
- Direct effects include:
- photoaging,
- DNA damage
- results in mutations of p53 tumour suppressor genes → therefore implicated in the development of melanoma and non-melanoma skin cancers
- carcinogenesis
Which skin cells work together to protect cells from UV DNA damage? [2]
- keratinocytes
- melanocytes
What are the complications of chronic UV exposure? [6]
- loss of skin elasticity,
- fragility,
- abnormal pigmentation
- haemorrhage of blood vessels
- wrinkles
- premature ageing
What are the Fitzpatrick skin colour types? [6]
- Very Fair
- always burns
- cannot tan
- Fair
- usually burns
- sometimes tans
- Medium
- sometimes burns
- usually tans
- Olive
- rarely burns
- always tans
- Brown
- never burns
- always tans
- Black
- never burns
- always tans
How would you describe this image in dermatology? [1]
Macule
How would you describe this image in dermatology? [1]
Papule
How would you describe this image in dermatology? [1]
Pustule
How would you describe this image in dermatology? [1]
Plaque
How would you describe this image in dermatology? [1]
Vesicle
How would you describe this image in dermatology? [1]
Bullae
How would you describe this image in dermatology? [1]
Erythematous
How would you describe this image in dermatology? [1]
Ulceration
What is acne? [1]
presence of comedones, pustules and nodules on the skin
Describe the pathogenesis of acne [6]
- Caused by chronic inflammation of the hair follicles and associated sebaceous glands
- Lining of the oil gland becomes thickened
- keratinocyte debris blocks sebaceous glands → more oil builds up → bacteria thrive off trapped oil → produces an inflammatory reaction (redness, swelling, pus)
Why is acne more common in puberty? [3]
Puberty is the period where androgens are high which causes more and thicker sebum to be produced, so the gland is more likely to get blocked
What are the clinical presenting features of acne? [8]
- Papules
- Pustules
- Comedones
- Erythema
- Nodules
- Cysts
- Scarring
- Hyperpigmentation in darker skin types
What are papules? [1]
small, raised spot on the skin, often dome-shaped and less than 5mm in diameter
What are pustules? [1]
small, pus-containing blister on the skin
What are comedones? [1]
blackhead = a plug formed of fatty material (sebum and keratin) in the outlet of a sebaceous gland in skin
What is erythema? [1]
flushing of the skin due to dilatation of the blood capillaries in the dermis
What are nodules? [1]
small swelling or aggregation of cells
What are cysts? [1]
an abnormal sac or closed cavity lined with epithelium and filled with liquid or semisolid matter
What areas of the body can acne be found? [6]
- Face
- Chest
- Back/shoulders
- Occasionally legs/scalp
What are the subtypes of acne? [7]
- Papulopustular
- Nodulocystic
- Comedonal
- Steroid induced
- Acne fulminans
- Acne rosacea
- Hidradenitis (acne inversus)
What is the name of the grading system used to grade severity of acne? [1]
the Leeds Acne Grading System
What are the treatment options for acne? [6]
-
Reduce plugging
- topical retinoid,
- topical benzoyl peroxide
-
Reduce bacteria
- topical antibiotics (erythromycin, clindamycin)
- oral antibiotics (tetracyclines, erythromycin)
- benzoyl peroxide reduced bacterial resistance
-
Reduce sebum production
- hormones: anti-androgen i.e. Dianette/OCP
What are the potential side effects of the following acne treatments?
- topical agents? [4]
- oral antibiotics? [1]
- OCP? [1]
- Topical agents:
- irritant,
- burning,
- peeling,
- bleaching
- Oral antibiotics
- gastro upset
- OCP
- possible DVT risk
What is isotretinoin, how does it work and what can it be used for? [3]
- Oral retinoid licensed for severe acne vulgaris
- Concentrated form of vitamin A
- Reduces sebum, plugging and bacteria
What are the side effects of oral isotretinoin? [8]
- Multiple side effects: most are trivial
- dry lips,
- nose bleeds,
- dry skin,
- myalgia
- Serious side effects
- deranged liver function,
- raised lipids,
- mood disturbance,
- teratogenicity
