Skin Flashcards
What is the main function of the epidermis?
Replace damaged cells to maintain the skins protective features
How does the epidermis protect the skin?
Produces keratinocytes and pushes them up through 4 layers of the epidermis until the cells are shed.
This takes 28 days
What does the epidermis consist of?
Keratinocytes, melanocytes and Langerhans cells
How many layers does the epidermis have? Name them
4 layers: Stratum basale Stratum spinosum Stratum granulosum Stratum corneum (top part)
Describe the stratum basale
Single layer of keratinocytes
Cells divide continually and push old cells up
Melanocytes produce melanin
Describe the function of the stratum spinosum
Anchors cells together by interlocking cytoplasmic processes
Describe the processes in the stratum granulosum
What does it contain?
Cells undergo enzyme induced destruction, losing nuclei and cytoplasmic organelles
Keratin is laid down
Contains lipid rich secretions - skin water sealant
Describe the stratum corneum
Layer contains dead cells flattened and filled with densely packed keratin
Cells are shed from skin
Describe the dermis
Located below the epidermis
Provides strength to skin, contains collagen and fibroblasts
Gives skin elasticity for strength
Has specialised structures e.g. sweat glands
What are the 7 skin functions
Production of vitamin D Sensory organ for touch, pain and temperature Controls body temperature Weak insulator Barrier protection Immune response Healing
Describe the function of skin in the production of vitamin D
7 dehydroxycholesterol produces vitamin D3 in the presence of sunlight
D3 is converted to calcidol in the liver and the hydroxylated to calcitrol in the kidney to produce active D3
Vitamin D increases plasma calcium levels by stimulating the intestinal epithelium to produce carriers for transport
What does a lack of vitamin D lead to?
Inadequate calcium absorption and deposition in the bones.
Causes rickets in children and osteomalacia in adults
Describe the function of skin as a sensory organ for touch, pain and temperature
Contains receptors which detect information from the skin surface and relay back to the CNS via sensory neurones
Mechanoreceptors can detect light touch and deep pressure on the skin surface
Thermoreceptors detect warmth and cold
Nocicereceptors respond to pain stimuli
Describe the function of skin in controlling body temperature
Capillaries in the skin control body temperature by altering blood circulation
Vasodilation causes capillaries to open and increase blood flow - causes heat loss at skin surface
Sweat glands in the skin secrete water and salt when internal body temp goes above normal
Describe the function of skin as a weak insulator
Mitochondria oxidise brown fat to produce more heat than ATP
Describe the function of skin as barrier protection
Protects from bacteria, toxins, dehydration, UV radiation, mechanical damage and trauma
Outer epidermal layer has keratinocytes which push up old dying cells - gives a waterproof layer
Describe the function of skin in an immune response
Produces new skin to replace old and damaged skin
Epidermis is first line defence barrier
Langerhans cells in the epidermis ingest foreign particles to be presented to the immune system
What are the 4 stages of healing? And briefly describe what happens in each.
- Haemostasis - clot formation
- Inflammatory processes - cleans wound to prepare for healing
- Proliferative phase - dermal repair and epidermal regeneration
- Maturation phase - scar formation
Describe the process of haemostasis in skin healing
Platelets in the blood recognise exposed collagen, platelets become sticking, releasing thromboxane A2
Platelets aggregate with collagen, forming a temporary plug
Activated platelets release serotonin which decreases blood supply to the wound
Damaged tissue releases thromboplastin which with calcium produces fibrin
Fibrin combines with the aggregate - traps RBCs to produce a clot
Describe the inflammatory process in skin healing
Langerhans cells are activated and release inflammatory mediators
Bradykinin increases pain at the site
Leukotrienes increase blood flow and warm the skin
Increased vascular permeability allows WBCs to reach
Plasma movement makes wound look swollen
Neutrophils digest bacteria and particles
Monocytes move to the wound
Describe the proliferative phase in skin healing
Macrophages release angiogenic growth factors for new blood vessels - in wound with low oxygen, it bring oxygen and nutrients
Chemicals attract granulation tissue to produce new connective tissue
Platelet derived growth factors and macrophages activate fibroblasts which grow and divide to produce a collagen network to provide strength
Myofibroblasts contract edges of the wound to close it. Cells move until the meet and then contact inhibition stops them moving
Describe the maturation phase in skin healing
Collagen is realigned to improve strength, the strands pull the wound inwards
Extra blood vessels close
What happens when a skin injury only affects the epidermis?
Keratinocytes in the stratum basale break from the basement membrane
Cells move till they meet each other, contact inhibitor stops cells moving
Give examples of intrinsic patient factors affecting wound healing
Nutrition Skin perfusion Age Weight Co-morbidity incl. medication Smoking
How does nutrition affect wound healing?
Protein is needed for antibodies, leukocytes, collagen and fibroblasts
Vitamin A, B, C, E, Zn and Fe are also needed
How does skin perfusion affect wound healing?
Wound need oxygen and nutrients, compromised blood supply can delay wound healing
How does age affect wound healing?
Younger people are more likely to have better perfusion, nutrition and less co-morbidities
How does weight affect wound healing?
In obesity, collagen structure may be altered and may decrease tissue perfusion
How do co-morbidities (incl. medication) affect wound healing?
Hypoglycaemia affects leukocyte phagocytosis
Anaemia, ischaemia, jaundice and malignancy
Some cytotoxic drugs and PGEIs precept healing due to antagonism of growth factors
Vasoconstrictors e.g. nicotine and cocaine cause tissue hypoxia
How does smoking affect wound healing?
Impairs wound contraction, decreases oxygen and causes platelet aggregation
Give examples of extrinsic wound factors affecting wound healing
Moist wound Temperature Oxygenation pH Infection Clean surface
How does moisture affect wound healing?
Wounds ned to be moist to allow epithlialisation
Moisture allows growth factors and enzymes to diffuse
But too moist encourages bacterial and fungal infections
How does temperature affect wound healing?
Wounds heal quicker at body temperature
How does oxygenation affect wound healing?
Less oxygen needed at granulation phase
More oxygen needed at epithelialisation
How does pH affect wound healing?
Decreased oxygen = increased lactic acid = decreased pH
Oxygen dissociated from Hb - this decreases tissue oxygenation
How does infection affect wound healing?
Delays wound healing, chronic wounds are colonised with bacteria.
Infection shows when bacterial cells outweigh the body’s immune response
How does a clean surface affect wound healing?
Foreign matter increases inflammatory phase and delays healing
What is the most common type of psoriasis?
Chronic plaque psoriasis
Which parts of the body does psoriasis commonly affect?
Scalp
Outside surfaces of the limbs - skin & elbows and lower back
What are the biological abnormalities of psoriasis?
Abnormal differentiation of keratinocytes - they don’t mature in the same way as normal ones
Infiltration of dermis and epidermis with activated T cells and neutrophils
Stimulation of cutaneous vasculature, leading to new blood vessel formation in psoriatic plaques
What other parts of the body can chronic plaque psoriasis affect?
Flexures Intertriginous areas (axillae, groin, perineum and under the breasts)
Describe the appearance of guttate psoriasis
Widespread small scaly lesions
Describe the appearance of pustular psoriasis
Yellow-brown pustules on palms or soles of the feet
What kind of psoriasis requires hospital administration?
Pustular
Describe erythrodermic psoriasis
Psoriasis that becomes inflamed
Scaling of skin
Skin feels hot but patient feels cold
Usually use to systemic or potent topical steroids so stop them
What kind of psoriasis appears on the nail?
Show as small pits, omycholysis and “oil spots” or “salmon patches”
Give examples of precipitating/exacerbating factors for psoriasis
Trauma Infection Hormonal events Sunlight Drugs Alcohol intake Cigarette smoking Psychological stress
What is classed as severe psoriasis?
Disease affecting >15-20% of body surface area (but this doesn’t factor in small areas or in sensitive or visible areas)
What is used to treat mild psoriasis?
Topical treatments
What is used to treat moderate to severe psoriasis?
Phototherapy, photochemotherapy or systemic drug treatment
How do emollients treat psoriasis?
Restore pliability of the skin and reduce shedding of skin scales. They reduce itching (pruritus) and help to prevent painful cracking and bleeding
Give examples of vitamin D analogues
Calcipotriol
Tacalcitol
Calcitriol
How do vitamin D analogues treat psoriasis?
Inhibit keratinocytes and differentiation
Anti-inflammatory activity
What makes calcitriol suitable for use on sensitive skin?
It is less irritating
Which areas of skin are mild topical steroids suitable for in psoriasis?
Face, flexures or genitalia
On which kind of psoriatic skin would potent steroids used for?
Recalcitrant lesions on trunk/limbs
How much skin can be covered by one FTU of a topical steroid?
2 palms worth of skin
Which topical corticosteroid should not be used in psoriasis?
Clobetasone butyrate 0.05%
What is Tazarotene?
Topically active retinoid
How does tazarotene treat psoriasis? How can its side effect be avoided?
Normalises keratinocyte differentiation and has anti-proliferative and anti-inflammatory effects
Use with a topical corticosteroid to minimise irritation
How does coal tar treat psoriasis?
Keratolytic with anti-inflammatory effects
What is dithranol?
Yellow irritating powder that causes inflammation, blistering and stains
What are the counselling points for psoriasis treatment?
Psoriasis can’t be cured but it can be controlled
Psoriasis is not infectious
Doesn’t develop into skin cancer
Can’t spread to new areas through topical treatment
What is involved in the management of atopic eczema in primary care?
Identify and avoid triggers
Care plan tailored to disease severity
Referral when conventional measures are ineffective
Give examples of tigger factors for eczema
Irritation
Psychological stress
Food hypersensitivity
Allergens
How do emollients treat eczema?
Restore/maintain or restore suppleness and pliability of the skin, they reduce corticosteroid requirements and improve cosmetic appearance
Form an oily layer over the skin that prevents water evaporation. Water trapped causes swelling of corneocytes which closes intercellular gaps
When should an emollient be applied with using with a steroid?
At least half an hour before any topical corticosteroid to avoid dilution or spread of the steroid
What is the purpose of humectants in emollients? Give examples of commonly used ones
They rehydrate dry and flaky skin
Urea, glycerin, PEG and lactic acid
What are the properties that colloidal oatmeal adds to an emollient?
Give an example of a product with colloidal oatmeal
Soothing and anti-pruritic properties
Aveeno cream
What property do lauromacrogols add to emollients?
Give examples of products with lauromacrogols
Balneum plus and E45 Itch
How do topical corticosteroids treat asthma?
Inhibit the production and action of inflammatory mediators, this reduced inflammation and itch
Give an example of a mild corticosteroid.
What kind of skin would it be used for?
Hydrocortisone
Thin skin
Give an example of a moderate corticosteroid
What is it used for and for how long?
Clobetasone butyrate
Used for mild-moderate eczema for 1-2 weeks
Give an example of a potent corticosteroid
What is it used for?
Mometasone furoate
Moderate-severe eczema and for areas where there is thicker skin
What should infants <1 y/o with eczema be treated with
Mild potency preparations e.g. hydrocortisone ointment 1%
What can be given OTC in community pharmacies for eczema?
Hydrocortisone 1% for mild-moderate atopic eczema but shouldn’t be used for >1 week without medical advice
Clobetasone butyrate 0.05% for short term use and for >12 y/o
What are the counselling points for eczema patients using corticosteroids?
Don’t use as an emollient
Make sure they know the difference between potency and concentration
One FTU for 2 palms worth of skin
When would antibiotics be needed in the treatment of eczema?
Give examples of the antibiotics used
Moderate-severe bacterial infection with S.aureus
Treat with oral antibiotics - flucloxacillin and erythromycin for a short period of time
How can sedating antihistamines be used in ecemza treatment?
Give examples
If taken at night they may help to reduce itching
Promethazine and alimethazine
When would topical immunomodulators be used in the treatment of eczema?
When there is a risk of serious side effects with topical corticosteroids or when eczema isn’t controlled with corticosteroids
Give examples of topical immunomodulators and the types of eczema they treat.
How do they work?
Pimecrolimus for mild - moderate eczema
Tacrolimus for moderate - severe eczema
They are both inhibitors of calcineurin phosphatase, an enzyme involved in the activation of T cells
Give examples of immunosuppressants used to treat severe atopic eczema
Ciclosporin
Axathioprine
Methotrezate
What needs to be measured before a patient is started on azathioprine?
Thiopurine methyltransferase enzyme activity
What is phototherapy and how does it work?
Controlled exposure to UV light, UVA or UVB
Involves immunosuppression
What kind of eczema is wet wrapping used for?
Describe the process
Extensive and severe eczema in young children
A layer of emollient or mild corticosteroid is applied and covered with a wet cotton tubular bandage, then a dry one. Can go to bed with it on.
What kind of counselling points should eczema patients be given?
Recognition of flares
Management of flares according to care plan
Importance of starting treatment for flares as soon as signs and symptoms appear and continue for ~48 hours after they subside
What is isotretinoin used for?
Severe acne unresponsive to topical treatments and oral antibiotics
How does isotretinoin work?
Reduces skin sebum excretion by ~90% after 6 weeks
Decreases hyperkeratinisation - interferes with comedogensis
Anti-inflammatory
What are the risks associated with isotretinoin use?
Teratogenic Depression, anxiety, suicidal ideation Impaired night vision Dry skin and mucous membranes Joint pains Makes skin sensitive (need UV protection)
What is psoralens used for?
When should it be taken?
How does psoralens work?
Psoriasis
Take 2 hours before UVA exposure, 3 times a week for 5-6 weeks
Disrupts DNA synthesis inhibiting basal cell proliferation
Slows basal cell growth to normal
What are the ADRs associated with psoralens use?
Teratogenic
Premature skin ageing
Skin pigmentation
Cataract formation
How does acitretin work?
Why would it be considered to be better than isotretinoin?
Decreases hyperkeratinisation - normalises skin cell proliferation and differentiation
Longer half life than isotretinoin
What are the risks associated with acitretin use?
Hyperlipidaemia
Hepatoxicity
How does methotrexate work?
Folic acid antagonist
Blocks DNA synthesis - slows down basal cell proliferation in psoriasis
Enzyme inhibition leads to increased adenosine which inhibits neutrophil chemotaxis and cytokine secretion
What are the risks associated with methotrexate use?
Liver cirrhosis (LFTs monthly) Blood disorders (FBC weekly then monthly) GI symptoms (5mg folic acid) Alopecia Infection risk
How does ciclosporin work?
Blocks calcineurin dependent factor
Interleukin 2 (IL2) is blocked
Blocks proliferation of T cells and cytosines
Blocks proliferation of keratinocytes
What are the risks associated with ciclosporin use?
Nephrotoxicity
Hypertension
Teratogenic
Infections
Give examples of biologics used in complex dermatology therapy
Etanercept Infliximab Adalimumab Usterkinumab Secukinumab
What are the risks associated with biologics?
Increased risk of infections
CVD risk
Worsening of neurological disease
Lymphoma
Which biologic are given as an IV infusion?
How often is it given?
Infliximab
0, 2, 6 then 8 weekly
Which biologics are given as a sub cut injection?
How often are they given?
Ethanercept - twice weekly injection
Adalimumab - every 2 weeks
Ustekinumab - 0, 4 then every 12 weeks
Secukinumab - weekly for 4 weeks, then every 4 weeks
