Skin Flashcards
what is vitilgo
autoimmune depigmentation (more noticable in darkskin)
describe the macroscopic structure of the human skin and how it varies between people
hair,thickness,colour,lety, oiliness
what is alopecia areata?
autoimmune hair loss
what is the effect of uv?
ages skin, causes basal cell carcinoma and malignant melanoma
what are the layers of the epidermis?
horny layer (strateum corneum) graular layer (stratum granulosum) prickle cell layer (stratum spinosum) basal layer (stratum basale)
describe the horny layer
top layer, flattened
no nuclei as dead cells (corneocytes)
protects underlying tissue from infection, dehydration, chemicals
describe the granular layer
below horny layer
keratinocytes migrating from stratum spinosum accumulate here
contain ktinolin granules filled with histadine and cystidine richproteins that bind the keratin filaments together
at transition between stratum granulosum and stratumcorneum, cells secrete lamellar bodies into extracellular space forming hydrophobic envolope responsible for skins barrier properties
when cells loose their nuclei nd organelles causing granular cells to become non-viable corneocytes in strateum corneum
describe the prickle cell layer
dark pink
spiny shape due to shrinking microfilaments
large, pale staining nuclei actively synthesising proteins
loose availability to divide
describe the basal layer
pale staining
keratinocyte mitosis occurs here, then moves to prickle layer
describe keratinocyte differentiation
occurs in the basal layer
migrate upwards towards prickle cell layer
keratinocytes synthesise keratin that strengthens the epidermis
describe epidermal dendritic cells (langerhans)
dendritic cells of bone marrow origin
scattered throughout prickle cell layer
highly specialised to present antigens to t lymphocytes
mediate immune reactions e.g. contact dermititis
describe melanocytes
dendritic cells of neural crest origin
occur at intervals along basal layer of epidermis
produce melanin (pigmentation)
produce more melanin in darker skin
what are the cellukar constituents of the dermis
fibroblasts - synthesise extracellular matrix
blood vessels
lymphatic vessels - bathe tissues with lymph
mast cells - part of immune system contains granules rich in histamine and heparin - allergy and anaphalais and protection
nerves - pain receptor
explain the components of the extracellular matrix
collagen - provide strength
elastin - elasticity
ground substance - granular extracellular material that binds components, binds water and hydrates skin
describe skin appendages
hair follicles, sebacs glands, sweat glands, nails
describe the main functions of the skin
barrier - outer stratum corneum forms major barrier preventing percutanous absorbtion of exogenous substances
sensation - nerves detect heat, pressure, contact - reflex minimises injury
thermoregulation - sweat glands and blood vessels allow regulation, subcutanous fat acts as insulation
Describe psoriasis
disrupted skin barrier leads to loss of fluid, nutrirnts and heat and excessive absorbtion of exogenous agents
Describe malignant melonoma
Malignant growth of melanocytes
Superficial above basement membrane
Penetrating modular = poor progress
Describe vitiligo
Autoimmune destruction of melanocytes - depigmentation
Describe alopecia areata
Autoimmune attack against hair follicles - loss of hair
Describe hairy skin
Stratified keratinised epithelium
Dermis with collagen bundles hair follicles sebacous glands and sweat glands
Vellus hairs - soft fine short pale everywhere
Terminal hairs - hard, coarse, large, long, dark
Describe palmar skin
Thick stratum corneum
Dermis
