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
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)
What is the name of the grading system used to grade severity of acne? [1]
the Leeds Acne Grading System
