Structure and Function of the Skin Flashcards
Describe skin
Largest organ in the body
Contains adnexal structures - hair, nails, glands and sensory structures
Important role in protection, homeostasis and transmission of sensations
What are the layers of the skin?
Skin - epidermis and dermis
Subcutaneous tissue below
Describe the process of cell development in the skin
- Stratum basale - cells divide by mitosis and some newly formed cells become superficial strata
- Stratum spinosum - keratin fibres and laminar bodies accumulate
- Stratum granulosum - keratohyalin and hard envelope form
- Stratum lucidum - dead cells lie within keratohyalin
- Stratum corneum - dead cells with hard protein envelope
Describe the nail anatomy
Hyponychium
Nail plate
Lateral nailfold
Nail bed
Lunula
Cuticle
Proximal nailfold
Nail matrix
What are the 3 stages of the hair cycle?
Anagen
Catagen
Telogen
What is the anagen phase?
Active growing phase
80-90% of hair
Where chemo effects
What is the catagen phase?
2-3 weeks phase growth stops/ follicles shrink
1-3% of hairs
What is the telogen phase?
Resting phase for 1-4 months
Up to 10% of hairs in a normal scalp
What are the functions of the skin?
Thermoregulation
Skin immune system
Barrier
Sensation
Vitamin D synthesis - UV light converts 7-dehydrocholesterol to cholecalciferol
Interpersonal communication
Describe the epidemiology of skin disease
22-30% of population affected
50% skin cancer/ lesions
25% require surgical procedure
Why is skin disease important?
Disfigurement, discomfort, disability, depression and death
What are some external causes of skin disease?
Temp., UV, chemical, infection and trauma
What are some internal causes of skin disease?
Systemic disease, genetics, drugs and infection
What are some cold injuries to skin?
Frostbite, chilblains, skin necrosis and cold urticaria
What is an example to trauma causing skin disease?
Dermatitis Artefacta - self induced trauma
What is an example of an autoimmune disease causing skin disease?
Bullous pemphigoid
What is a macule and a patch?
Macule -Small flat circumscribed area
Patch - larger flat circumscribed area
What is a papule and a plaque?
Papule - small raised area
Plaque - larger raised area
What is a vesicle and a bulla?
Vesicle - small fluid filled
Bulla - large fluid filled
What is a pustule and an abscess?
Pustule - small pus filled
Abscess - large pus filled
What is a erosion and an ulcer?
Erosion - loss of epidermis
Ulcer - loss of epidermis and dermis
Describe a macule
Non-palpable change in skin colour with distinct borders
Describe a papule
Solid lesion less than 1cm in diameter
Describe a nodule
Palpable lesion more than 1cm in diameter which is taller then it is wide
Ex. neurofibromatosis and rheumatoid nodules
What is an example of an erosion?
Toxic epidermal necrolysis - severe drug reaction
What is an example of an ulcer?
Pyoderma gangerosum
What is distribution?
How skin lesions are scattered or spread out
May be isolated or multiple
Localised, generalised, symmetrical…
What are the most common skin conditions?
Acne, psoriasis, rosacea, skin lesions, urticaria, warts, leg ulcers, scalp/ nail disorders, eczema and infections
What are some conditions which can have cutaneous signs?
Erythema nodosum, sarcoidosis, vasculitis, malignancy and auto-immune conditions
What is a skin change which shows hyperlipidaemia?
Eruptive xanthoma
Describe acanthosis nigricans
Associated with insulin resistance, obesity and malignancy
Flexural distribution
Hyperkeratosis and hyperpigmentation papules
Velvety appearance
Describe thyroid skin disease
Pretibial myxoedema
5% of Graves disease
Same process behind eyes - mucinosis
What are some investigations in dermatology?
Bacterial infection - charcoal swab and ask for MC&S (microscopy, culture and sensitivities)
Viral - Swab for PCR, swab vesicle, and throat swab
Fungal - skin scrapping, nail clipping and hair sample
What is a simple way to take a skin biopsy?
Punch biopsy
Takes all 3 layers of the skin
Numb with local anaesthesia
