GEP (Life Structure) Week 5 Flashcards
What is the function of Skin
Functions:
* It’s your barrier to microorganism
* Stops you evaporating - keratinised dead layer of squamous epithelium + oily sebum makes you watertight
* Prevents infection – Sebum chemicals, skin pH ~4.7
* Excretion/ Absorption - sweat, heat, (topicals/ patches)
* Melanocytes (basal epidermis) protect from UV, Keratinocytes of epidermis use UV to activate Vit D
* Sensation – mostly nerves in the dermis/ hypodermis
* Changes shape – growth, pregnancy, callouses
Function:
Largest organ in body by surface area –Severe burns/ skin damage can consequently lead to: Infection, which can go into bloodstream – sepsis, fluid loss, including low blood volume (hypovolemia), electrolyte imbalance, hypothermia, all of which can be fatal.
Protection (part of adaptive immune system); The skin provides protection to the body in various ways.
*Keratin protects underlying tissues from microbes, abrasion, heat, and chemicals, and the tightly interlocked keratinocytes resist invasion by microbes.
*Lipids released by lamellar granules inhibit evaporation of water from the skin surface, thus guarding against dehydration; they also block entry of water across the skin surface during showers and swims.
*The oily sebum from the sebaceous glands keeps skin and hairs from drying out and contains bactericidal chemicals (substances that kill bacteria).
*The acidic pH of perspiration inhibits the growth of some microbes.
*The pigment melanin helps shield against the damaging effects of ultraviolet light.
thermoregulation (eccrine sweat glands aid heat loss with blood vessel dilation – constriction of vessels conserve heat – erector pili muscles control hair and provide some insulation);
sensation;
controls fluid loss and stores lipids, also helps with vitamin D synthesis;
water resistance (helped by Stratum Granulosum releasing sebum)
also absorbs O2, nitrogen and CO2.
What are the 3 layers of the skin
Epidermis
Dermis
Hypodermis
Epidermis: stratum corneum, stratum lucidum (only in thick skin), stratum granulosum, stratum spinosum, stratum basale
Dermis: connective tissue made up of fibroblasts, which produce and secrete extra cellular matrix eg collagen and elastin
Hypodermis: Fat storage, cushioning
Pilosebaceous unit: hair follicle, erector pili muscle, sebaceous gland, apocrine sweat glands.
What are the layers of the epidermis
Epidermis – outermost layer, composed of stratified squamous epithelium, with layers of keratinocytes which derive from the ectoderm. Also contains hair shafts. There are five sublayers of the epidermis. Epidermis is avascular.The keratinocytes typically die during their time in the Stratum Lucideum due to lack of oxygen and nutrients
The epidermis is composed of keratinized stratified squamous epithelium. It contains four principal types of cells:
Keratinocytes: 90% of epidermal cells. Keratin is a tough, fibrous protein that helps protect the skin and underlying tissues from abrasions,heat, microbes, and chemicals. Keratinocytes also produce lamellar granules, contain cholesterol, fatty acids and proteases which play a role in keratinization and maintaining the barrier functions of the skin. They release a water-repellent sealant that decreases waterentry and loss and inhibits the entry of foreign materials.
Melanocytes: mostly found in the stratumbasale (deepest layer). They’re derived from the ectoderm and they produce melanin pigment, which shields against UV light damage
Intraepidermal macrophagesor Langerhans cells (arise from red bone marrow and migrate to the epidermis). Involved in immune responses mounted against microbesthat invade the skin and are easily damaged by UV light. Their role in the immune response is to help other cells of the immune system recognize an invading microbe and destroy it. They are found in all layers of the epidermis, but predominantly in the stratum spinosum.
tactile epithelialor Merkel cells are located in the deepest layer of the epidermis. They are oval-shaped mechanoreceptors essential for light touch sensation– found in the skin.They contact the flattened process of a sensoryneuron (nerve cell), a structure called a tactile disc or Merkel disc.
What is the dermis and the layers in the dermis
Dermis – Connective tissue made up of fibroblasts, which produce and secrete collagen. Originates from the mesoderm (except facial dermis which comes from the neural crest) Composed of two layers – a thin papillary layer below the stratum basale and a deeper reticular layer. The papillary layer is more superficial and contains a thinner arrangement of collagen fibres. Unlike the epidermis, the dermis is rich in blood vessels, lymphatics, nerves and sensory receptors.
The papillary contains macrophages which capture pathogens that make it past the epidermis. Also contains fibroblasts which produce collagen. The fibroblasts are arranged in finger-like projections called papillae; each of which contains blood vessels and nerve endings:
*Meissner corpuscle - this is a disk shaped structure that detects fine touch.
*Dendrites that detect pain.
The reticular layer of the dermis is even thicker than the papillary layer. Also contains fibroblasts with scattered macrophages. But the collagen in the reticular layer is packed very tightly together, to provide tissue support. In addition, fibroblasts in the reticular layer secrete elastin–which is a stretchy protein that gives skin its flexibility.
The reticular layer also contains the skin’s accessory structures like oil and sweat glands, hair follicles, lymphatic vessels, and nerves - and all of the blood vessels that serve these tissues.
Type of nerve ending found here is called a Pacinian corpuscle - this is an onion shaped structure that detects pressure or vibration.
Since the reticular layer contains lots of blood vessels and sweat glands, it’s also largely responsible for regulating temperature.
Pilosebaceous unit: hair follicle, erector pili muscle, sebaceous gland, apocrine sweat glands.
What is the hypodermis
Also known as the subcutaneous layer
Contains adipose tissue for cushioning, thermoregulation, and as an energy store
The target of subcut injections – has high vascularity and good drug absorption
As you age, the hypodermis shrinks, and your skin begins to sag
If larger amounts of fat accumulate in the hypodermis, you can see the appearance of cellulite – pockets of fat that push against the connective tissue and give skin a bumpy appearance
The hypodermis also has nerves passing through, potentially some mechanoreceptors involved in proprioception (though these are mainly from detectors in tendons and muscle)
Not a question
Vitamin D Revision
10 micrograms per day is the recommended Vit D for a person in the UK. Due to low sunlight year-round, it may be a good idea to supplement
Individuals with darker skin produce less vitamin Dwith the same amount of sunlight exposure than individuals with lighter skin colour
Low Vit D can lead to Rickets (children) or Osteomalacia (adults)
What is a macule skin lesion
Macule
Macule – one
Macular rash – lots of macules
A well-circumscribed lesion with change in skin colour only (not raised or palpable) Varies but mostly considered to be <10mm
They can be:
Hyper-pigmented (darker than surrounding skin) i.e. mole
Hypo-pigmented paler i.e. vitiligo
Erythematous
Crusty
Signs a mole could be cancerous include if it is itching, painful, inflamed, dark brown centre with lighter, uneven edges. Moles over 8mm diameter are higher risk
Birth marks can include:
Macular stains
Hemangiomas
Port-wine stains
Café-au-lait spots
Mongolian spots
Moles
Discribe patch (type of skin lesion)
Describe Papule (skin lesion)
Describe nodule (Skin Lesion)
Describe plaque (skin lesion)
Describe blister (Skin Lesion)
Fluid is usually serum
Summary of skin lesion Definitions
What are the other types of skin presentations
e.g. Meningitis often has a non-blanching petechial or purpuric rash. Starts small and gets larger, can be harder to spot in darker skin
N.B. Ecchymosis is flat pooling of blood under the skin from either trauma or metabolic problems, while a hematoma is a larger collection of blood outside of blood vessels that’s typically raised and causes pain to the touch, always caused by trauma.
What are the different rash distribution
Psoriasis can also be in flexor areas (e.g. in Flexor psoriasis), and eczema can be on extensor surfaces, but these are less common presentations
What does Adverse drug affect mean
What is the risk factor and aetiology of Psoriasis
What are the DDxs for a red scaly rash
What is the pathophysiology of Psorasis
What are the different types of Psoraisis
Chronic Plaque psoriasisfeatures the thickened erythematous plaques with silver scales, commonly seen on the extensor surfaces and scalp. The plaques are 1cm – 10cm in diameter. This is the most common form of psoriasis in adults.
Guttate psoriasisis the second most common form of psoriasis and commonly occurs in children. It presents with many small raisedpapulesacross the trunk and limbs. The papules are mildly erythematous and can be slightly scaly. Over time the papules in guttate psoriasis can turn into plaques. Guttate psoriasis is often triggered by astreptococcal throat infection, stress or medications. It often resolves spontaneously within 3 – 4 months.
Flexural/Inverse psoriasis: This affects folds or creases in your skin, such as the armpits, groin, between the buttocks and under the breasts. It can cause large, smooth red patches in some or all these areas.
Inverse psoriasis is made worse by friction and sweating, so it can be particularly uncomfortable in hot weather.
Pustular psoriasisis a rare severe form of psoriasis where pustules form under areas of erythematous skin. The pus in these areas is not infectious. Patients can be systemically unwell or it can be localised to palms, soles, fingers, toes. It should be treated as a medical emergency and patients with pustular psoriasis initially require admission to hospital.
Erythrodermic psoriasisis a rare severe form of psoriasis with extensive erythematous inflamed areas covering most of the surface area of the skin. The skin comes away in large patches (exfoliation) resulting in raw exposed areas. It should be treated as a medical emergency and patients require admission.
What are the clinical features of Psoriasis
As mentioned before, the skin is a part of ourself that most people see and judge, and so there are psychosocialimplications with chronic skin lesions. They can affect mood, self-esteem, and causeself-isolation, depressionandanxiety
What is the management for Psoriasis
What are the 1+2 step of the managment for Psoriasis
Emollients: general umbrella term for topical moisturizers - they soothe skin and reduce the amount of scale. Ointments – more oil based, cream and lotion more water based. Oil based products stay on the skin longer – more effective – and don’t tend to have preservatives in them. But they also have poorer compliance as they’re messy.
Steroids: side effects: skin atrophy if used long term, striae, acne, Cushing’s syndrome. Combination often used: Dovobet or Enstilar
Vit D analogues: (anti-proliferative, reduces keratinocyte proliferation which reduces scaliness) – Calcipotriol.
What is the 3 step of Psoriasis managment
UVA and UVB:
UVA rays can penetrate your skin more deeply and cause your skin cells to age prematurely. About 95 percent of the UV rays that reach the ground are UVA rays. The other 5 percent of UV rays are UVB. They have higher energy levels than UVA rays, and typically damage the outermost layers of your skin, causing sunburn.
What is the 4+5 step of Psoraisis management
Methotrexate can be prescribed to women of childbearing age but must check if sexually active/on contraception
For Biologic therapy, you must have severe psoriasis, classed as a score of ≥10 PASI and >10 DLQI
Must have tried systemics/ have a reason why they can’t take systemics.
There are lots of biologics:
Adalimumab/Etanercept/Golimumab/Infliximab:
Anti- TNFa
Rituximab - Causes B cell depletion
Abatacept - T cell costimulation inhibitor
Toculizumab - IL-6 inhibitor
Baricinib - JAK inhibitor
Anakinra - IL-1 receptor antagonist
