1379190
Description
Flashcards by Hannah Tribe, updated more than 1 year ago
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Created by Hannah Tribe
over 9 years ago
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| Question | Answer |
| Give 4 main functions of skin | Metabolism Thermoregulation Sensation Barrier |
| How is the skin involved in metabolism? | It is a store of adipose tissue and synthesises vitamin D |
| How is the skin involved in thermoregulation? | Blood supply to the skin can be altered to allow/prevent heat loss, and the underlying adipose layer acts as insulation |
| How is the skin involved in sensation? | Lots of nerve endings in the skin to give sensations of pain, temperature, pressure and touch |
| What is the skin a barrier from? | Physical, chemical and biological threats |
| What are the 2 basic layers of skin? | Epidermis Dermis |
| What are the 4 layers of the epidermis, from superficial to deep? | 1. Stratum corneum 2. Stratum granulosum 3. Stratum spinosum 4. Stratum basale |
| What other layer could there be? Where might it be found in the body and between which layers is it? | Stratum lucidum, on thick skin only, appears as a clear layer between the corneum and granulosum |
| What are the characteristics of the stratum corneum? (3) | 1. Anucleated cells 2. Made of 'soft' keratin = keratinised cells + lipids 3. Cells are lost by wear and tear at the surface |
| What are the characteristics of the stratum granulosum? | 1. Keratinohyaline granules (pre-keratin, will become surface keratin) 2. Lamellar bodies (lipids, provide waterproofing for surface) |
| What are the characteristics of the stratum spinosum? (2) | 1. Cells connected by desmosomes to create spiny, strong layer 2. Contains Langerhans cells |
| What are the characteristics of the stratum basale? (3) | 1. Keratinocytes are produced here 2. Merkel cells here 3. Melanocytes produce melanin here |
| What are desmosomes? | Connections made between cells to provide mechanical support, formed by 2 plaques inside each cell connected to the cell cytoskeleton, which bind to each other by cadherins. |
| What are Langerhans cells? | Antigen-presenting cells |
| What are Merkel cells? | Thought to be involved in sensory functions involving touch |
| What are the 2 types of melanin? | 1. Eumelanin, which appears brownish/black and determines skin and hair colour 2. Pheomelanin, which appears red/yellow and is also involved in determining hair colour |
| What is directly underneath the stratum basale? | A Basement membrane, connected to the basale layer by desmosomes. |
| What are the arrows pointing to and what are they? | 1. Dermal papillae, which are upgrowths of the dermis into the epidermis, providing the epidermis with capillaries 2. Rete ridges, which are downgrowths of the epidermis into the dermis Both give a convoluted basement membrane and add stability |
| How do friction blisters form? | Constant friction of the skin causes crushing of the cells in the stratum spinosum, and results in a build up of fluid within this layer. |
| What is vitiligo? | A skin disease in which skin appears to lose its colour, usually starting around the digits (e.g. black person with white fingers) |
| What are the 2 basic layers of the dermis? | 1. Upper papillary dermis 2. Lower reticular dermis |
| What can be found in the dermis? (6) | 1. Fibroblasts and their matrix 2. Glycosaminoglycans (GAGs) 3. Blood vessels 4. Nerves 5. Lymphatics 6. Immune cells |
| What is found in the upper papillary dermis? | The superficial plexus of vessels |
| What is found in the deep reticular dermis? | More of the superficial and a deep vascular plexus |
| How is blood flow to the skin controlled? | Sympathetic innervation to arteriovenous anastomoses (AVAs) running between the arteries and veins between the superficial and deep vascular plexuses allows blood flow to be limited by constricting some of the anastomoses. |
| What are the 2 main types of nerve supply to the skin? | 1. Non-myelinated sympathetic neurons that control sweat glands, arrector pili muscles and blood flow 2. Sensory afferents |
| What different types of sensory fibres could be found in the dermis? (5) | 1. Free nerve endings that sense pain, temperature and pressure 2. Hair follicle receptors, which detect touch of the hairs 3. Meissner corpuscles which are present on hairless skin and detect touch 4. Pacinian corpuscles which are fast-adapting sensors of pressure 5. Ruffini endings and Merkel cells which are slow-adapting sensors of touch |
| What is below the dermis and what can be found there? | The subcutis, which is mainly adipose tissue, containing vessels and nerves |
| What is the function of it? (3) | 1. Acts as a shock absorber 2. Provides heat insulation 3. Store of adipose can be used in energy metabolism |
| Where does hair growth begin? | At the hair bulb, the deepest part of the hair follicle, in the dermis |
| What are the characteristics of the hair bulb? (2) | 1. Highly vascularised 2. Contains actively dividing epithelial cells |
| Why are hair and nails hard, yet skin is soft? | Hair and nails do not have the stratum granulosum which produces the lipid component of skin that makes it soft, so is purely hard keratin |
| What surrounds hair follicles and what is its function? | Arrector pili smooth muscle, controlled by sympathetic innervation so contracts when cold or scared, causing hairs to stand erect |
| What glands are associated with hair follicles? | Sebaceous glands |
| What is their function? | Sebaceous glands produce sebum which is a holocrine secretion, and this is an oily substance that helps keep the skin waterproof and moisturised |
| Name 2 types of sweat gland present in the skin. | 1. Apocrine 2. Eccrine |
| What general structure do sweat glands have? | Coiled and tubular |
| Where are apocrine glands found? | In the axilla and groin regions |
| Where are Eccrine sweat glands found? | All over the body, except the palms of the hands and the soles of the feet |
| What are the differences between apocrine and eccrine sweat glands? (4) | 1. Apocrine only exist in axilla and groin regoins 2. Apocrine glands usually discharge sweat into the hair follicles, eccrine go straight to the surface 3. Apocrine glands produce sweat which smells, due to the mixture of sweat with the bacteria on the skin in these areas, causing metabolism 4. Apocrine glands are under adrenergic sympathetic control (NA, adrenaline) whereas Eccrine glands are under cholinergic sympathetic control (ACh) |
| What are 2 simple functions of vitamin D? | 1. Regulate calcium metabolism 2. Regulate phosphate metabolism |
| What does vitamin D deficiency lead to? | Rickets (in children), osteomalacia (in adults) |
| Give 3 reasons why death might occur following extreme epidermal damage? | 1. Become dehydrated and go into shock 2. Infections can enter and become systemic (e.g. sepsis) 3. Extreme heat loss causing hypothermia |
| Give 5 environmental insults to the skin | 1.Radiation (e.g. UV) 2. Allergens (e.g. latex) 3. Irritants (e.g. cleaning products) 4. Microbes/parasites 5. Physical insults (trauma, burns etc,) |
| How does the skin adapt itself to friction? | The corneum becomes thickened due to hyperkeratosis (more layering of keratinocytes) - occurs on surfaces such as the feet or fingertips |
| How does the skin adapt itself to protect against UV radiation? | Melanocytes in the basale layer produce melanin (the pigment giving skin colour), which protects against DNA damage by the UV rays of the sun (thus protecting against skin cancer and sunburn) |
| What are the features of melanocytes? (2) | 1. They are found in the basale layer of the epidermis, and have many dendrites extending to other cells in the epidermis 2. They contains many melanosomes (granules containing melanin) which they transfer to the keratinocytes in the basale layer along the dendrites |
| What is the destination of the melanosomes and what is their purpose? | They are transferred to the keratinocytes, where they form a melanin cap over the cells, protecting the stem cell DNA within them |
| How does UV damage cause extra protecting against UV radiation? | UV damage to DNA stimulates the melanocytes to produce more melanin, which has a protective role over the stem cell DNA in basale cells |
| How is this adaptation visible? | Causes a tan |
| What is the term for extreme hyperkeratosis? What is the cause of it? | Lichenification, due to excessive friction (rubbing of tight clothes or itchy skin conditions etc.) |
| What are the levels of UV radiation emitted from the sun and what is the difference between them? | UVA, UVB and UVC - classified according to their wavelengths. UVC has the shortest wavelength and is blocked by the ozone layer. Some UVB is transmitted through the ozone, whereas most of UVA (the longest wavelength) is transmitted through and reaches the Earth's surface. |
| What is sunburn and what are the risks of it? | Sunburn is radiation damage from the sun's UV rays, causing DNA damage in the skin, with the potential of causing skin cancer |
| Why do people tend to get wrinkles when they are exposed to the sun for prolonged periods of time? | UVA radiation causes solar elastosis, damaging the skin cells and causing them to lose their elastin and therefore go wrinkly |
| What is the scientific name for moles? | Naevi (naevus singular) |
| How are moles formed? | Moles are large groups of proliferating melanocytes, but are usually benign |
| What is the scientific name for freckles? | Ephelides |
| How do people get freckles? Are there any risks? | There is a genetic component that causes people to have freckles, as well as it being associated with fair hair. They appear in areas exposed to the sun, and carry an increased risk of melanoma |
| What are 'age spots'? | 'Solar lentigos' - age-related, benign markings |
| What is another risk of UV radiation on the skin? | Solar keratoses - abnormal growths of keratinocytes (often on the scalp of bald people, for example) which are usually benign but have the potential to become cancerous |
| What are the 2 main types of skin cancers and which cells do they involve? | 1. Melanoma, involving melanocytes 2. Non-melanoma, involving keratinocytes |
| What are the 2 sub-types of non-melanoma? | 1. Squamous cell carcinoma 2. Basal cell carcinoma |
| Why are melanomas so dangerous? | They can spread rapidly all over the body, metastasising in other organs |
| What is UV radiation on the skin useful for? | Vitamin D production |
| What are the 2 main types of contact dermatitis? | 1. Irritant 2. Allergic |
| How does allergic contact dermatitis arise? | Langerhans cells in the skin present allergen to the immune system as a threat, so a response is initiated. This causes memory T cells to be made so that on subsequent exposures, a hypersensitivity reaction occurs |
| What is the scientific name for a fungal/bacterial nail infection? | Paronchyia |
| Give 2 examples of bacterial skin infections | 1. Impetigo 2. Cellulitis |
| Give an example of a viral skin infection | HPV (warts) |
| How can infections enter the skin? Who is more likely to get skin infections? | Through cuts/abrasions (anything which has disrupted the epidermis) - people with impaired immunity are more prone to such infections (HIV etc.) |
| What is the cause of atopic eczema? | A defect in the barrier function of the skin, causing it to be more susceptible to irritaiton from allergens and other environmental insults |
| What occurs in the acute stage of atopic eczema? | Swelling in the epidermis, causing vesicle formation (blistering) |
| What occurs in the chronic stage of atopic eczema? | Hyperkeratosis causes a thickening of the epidermis |
| Where is commonly affected by atopic eczema? | Flexor surfaces such as the inside of the elbow, knees, eyelids etc. |
| Why does itching cause more of an itch? | Initial itching due to dryness of the skin in eczema causes cells to release histamine, which makes them feel more itchy |
| What treatments can be given for eczema? | 1. Topical creams/emollients to moisturise the skin and protect it 2. Topical steroids during flare-ups (for maximum 7 days in each month) |
| What can be caused if eczema is co-infected with herpes virus? | Eczema herpeticum |
| What is psoriasis? | A chronic, inflammatory state in which the turnover of cells in the epidermis is rapidly increased, causing the build up of cells forming plaques |
| How does psoriasis differ from eczema? | Psoriasis affects the extensor surfaces, whereas eczema affects the flexor surfaces |
| What are the treatments for psoriasis? (7) | 1. Topical steroids 2. Emollients for moisturisation 3. Phototherapy 4. Coal Tar (to slow cell proliferation) 5. Salicylic acid (to break down keratinocytes) 6. Vitamin D analogues (calcipotriol, slows cell proliferation0 7. Systemic immune suppression (methotrexate, acetretin, ciclosporin etc.) |
| What causes acne vulgaris? | Overactivity of the sebaceous glands causes hair follicles to become blocked, also with a bacterial infection |
| What are the 2 aims of treatment of acne vulgaris? | 1. To reduce the amount of oil in the skin 2. To remove the bacterial infection |
| What is impetigo? | Bacterial skin infection which is very contagious and common in children. It can be a result of bacterial co-infection with eczema |
| What causes viral warts? | HPV |
| What is tinea? | Fungal infection (ringworm) that causes a scaly, annular, slowly enlarging plaque |
| How is it treated? | With anti-fungals |
| What is actinic keratosis? | A hyperkeratotic lesion which was induced by the sun, which has the potential to become cancerous |
| What can be the prognosis of actinic keratosis? | As it penetrates deeper through the layers of skin it first becomes Bowen's disease and then becomes a squamous cell carcinoma |
| What is the other type of carcinoma that can develop in the skin? | Basal cell carcinoma |
| How is it treated? | Surgical excision, although does not usually metastisise. |
| What is the ABCDE of suspicious pigmented lesions? | A- assymetry B- border irregularity C - colour variation D - diameter >6mm E - extra features such as bleeding, itching |
| What is the consequence of finding suspicious pigmented lesions? | Patients are referred to a hospital clinic within 2 weeks (2 week wait rule) |
| What is Breslow thickness? | The distance in millimeters between the upper layer of the epidermis and the deepest point of penetration of a tumour |
| How is it significant? | The prognosis is better is the tumour is thinner |
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