SKIN

• It consist of Skin & Accessory organs (hair, nails & gland)

• It is the largest sense organ

• Forms a barrier between internal & external environment.

• The weight is 8-10 pounds, total surface area is 22 Sq.ft.

• Thin on ventral surface & thinner on dorsum

• Functions:

Protection

Sensation

Secretion

Temperature regulation

Integumentary system

Structure of Skin• It consist of 3 layers

Epidermis

Dermis

Subcutaneous

Epidermis:consist of two layersStratum CorneumBasal layer: cell formation,

Melanocyte=melanin=protects from UV light

• Dermis(cornium): below epidermisConsist of blood & lymph vessels, nerve cellsAccessory organ: Hair follicle, Sweat & sebaceous

glandSupporting tissue: Connective (elastic &

Collagen) , fibrous tissueStretch Mark: In women after child birth because of

breakdown of elastic & collagen fibres.• Subcutaneous tissue: contains lipocytes, which

manufacture & store fat thus protecting and insulating deeper tissue

Colors of Skin

• White: Leukoderma, e.g palms & soles

• Black: Melanoderma, e.g all our body

• Blue: Canoderma, e.g VSD, Varicose vein

• Yellow: Xanthoderma. e.g Jaundice

• Red: Erythroderma, e.g skin of lip

Accessory organ• Hair: made up of cells of epidermis , but are

filled with keratin, melanocytes lie at the base, grow at a rate of ½ inch a month

• Nails:made of hard keratin material, grow at a rate of 1mm /week, finger>toe nail

• Sebaceous gland:secrete oil called sebum, overproduction leads to acne & blackheads

• Sweat gland:all over body, more over palm & soles, open by ducts as pore.

Skin/cutaneous lesion: It is a localized area of damage to tissue by disease or trauma

• Albinism:congenital absence of melanin• Anhidrosis: genetic condition of inability to sweat• Atheletes foot:superficial skin infection of foot

• Alopecia:localised loss of hairs• Burns:injury to tissue by heat, electrical, chemical

Types:

Ist degree:superficial epidermal lesion, e.g sunburn

2nd degree: epidermis & dermis

3rd degree:all the layers are damaged

Burns severity is measured in terms of percentage of affected area• Callus: area of hardened & thickened skin, seen at pressure site• Carbuncle:painful inflammation of subcutaneous tissue with pus• Comedo:sebaceous material over duct of sebaceous gland,e.g. blackhead• Corn:conical thickening of skin over toe joint & between toes• Cyst: sac containing fluid or semisolid material, e.g sebaceous& pilonoidal cyst• Dermabrasion:removal of acne, scar, tattoo• Dermatome:instrument to cut skin for grafting

• Eczema:inflammation of skin, charact. by redness, oozing, crusting & scaling• Electolysis:hair removal by electric current• Erythema:redness of skin• Ecchymosis:bluish black mark on skin, e.g IIry to injury• Fissure:groove or crack in skin, e.g anal fissure• Furuncle:a boil, abcess from infection of hair follicle• Macule: flat discoloured lesion, e.g flat mole, tattoo, freckles• Nevus:pigmented flat area, present since birth, e.g mole, birthmark• Papule: small round elevation, size pinpint to pea, e.g peas• Pustule:elavation with pus• Polyp:tumour on the stem, found on mucus membrane, e.g nasal polyps• Pruritis: itching• Petechiae: small pin point haemorrhage over skin• Intradermal:Inside skin• Urticaria: acute allergic reaction, red round wheals on skin• Ulcer: large erosion of skin/mucus membrane• Vesicle/blisters: small collection of clear fluid• Vitiligo: loss of pigment in areas of skin• Wheal: smooth elevated edematous area, e.g allergy, mosquito bite

Disorder of skin• Acne:inflammation of sebaceous gland,ocurs during puberty, because of

hormonal changes and infection, four basic lesion are comedones,papules, pustules & cyst, treated by antibiotics & accutane

• Impetigo: superficial skin infection caused by staphylococci/streptococci

• Systemic lupus erythematosus(SLE):autoimmune inflammatory disease, occurs in young women, associated with other connective disorder e.g rheumatoid arithritis, rheumatic fever. Characteristic butterfly lesion over face, treated with immunosuppressive & corticosteroids

• Psoriasis:chronic disease characterized by reddish, slightle raised plaques or papules covered with scales, involving scalp, elbow, knee back & buttocks, treatment by topical lubricant, keratolytics, steroid, PUVA

• Decubitus ulcer/bedsore/trophic ulcer: seen in patients who are bedridden, seen over sacrum, heels, ankles, buttocks.

• Warts:caused by virus causing epidermal growth, seen on genitals, anal

• Cold sore/fever blister: secondary to fever

• Sunburn: due to prolonged exposure of skin to UV light

• Scabies:caused due to parasite(mite)

• Scleroderma: chronic progressive thickening of skin.

• Gangrene: death of skin IIry to DM

Skin neoplasm

• Benign: Leukoplakia, nevus , warts

• Malignant:

Basal Cell carcinima:malignany of basal cell layer

Kaposki sarcoma:malignant vascular nodule

Malignant melanoma:cancerous growth of melanocyte

Squamous cell carcinoma: malignant tumor of squamous epidermis

Drugs associated with skin lesion

• Keratolytic agents:salicyclic acid, tretinoin & benzyl peroxide• Depilatories:calcium hydroxide, calcium thioglycollate, strontium hydroxide• Caustics:glacial acetic acid & trichloroacetic acid• Astringents:aluminium salt• Dusting powder: talc, magnesium oxide• Protective dressings: colloidon• Corticosteroids; hydrocortsone, prednisone, deflazacort• Sunscreening agents:

Laboratory test: Abbreviations:

Fungal scrapping DLE:discoid lupus erythematosus

Skin biopsy PPD:purified protein deravative

Skin test PUVA:psorlen ultraviolet light theraphy

Procedures: SLE:systemic lupus erythematosus

Cryosurgery bx: biopsy

Skin biopsy subq: subcutaneous