Skin Flashcards
skin general main role:
tough, tensile strength, covers the whole body, protection from friction/impact, UV rays
skin functions:
external layer relatively impermeable to water, thermoregulation, immune function
- makes vit D3, secretes oil, sweat
- receptors: touch, heat, pressure and pain
main layers of skin and composition:
epidermis and dermis, btw is basement membrane
- epidermis: keratinised stratified squamous epithelium
- dermis: deep connective tissue
hypodermis/ subcutaneous layer: areolar and adipose tissue
layers of epidermis and cell types found:
stratum: corneum, lucidum, granulosum, spinosum, basale (from superficial-deep)
mainly keratinocytes, also melanocytes, intraepidermal macrophages (Langerhans cells) and tactile (Merkel’s cells)
stratum basale: cell type/ composition/ features/ function
LIVING: simple basal columnar or cuboidal cells -> dermal/epidermal junction
- frequent mitotic cells, constantly renewing keratinocytes
- every 15-30 days
stratum spinosum: cell type/ composition/ features/ function
LIVING: prickle cell/ spiny layer (8-10 layers)
- cuboidal/ polyhedral
- or slightly flattened keratinocytes w/ nucleus and cytoplasm filled with bundles of keratin (strength, resistance)
- thick in areas of friction and pressure
stratum granulosum: cell type/ composition/ features/ function
DEAD: 3-5 layers of flatterned polygonal keratinocytes, cytoplasm filled with coarse basophilic granules
- cells undergo apoptosis
- also has small lamellar granules, fuse with cell membrane-> discharging contents into intercellular spaces= lipid-rich sheets (seals skin, barrier)
stratum lucidem: cell type/ composition/ features/ function
DEAD: 3-5 layers of translucent flattened cells, no evident nuclei/ organelles
- densely packed keratin filaments, thick plasma membrane
stratum corneum: cell type/ composition/ features/ function
DEAD: cornified (keratinised)
- varies thickness (15-20, up to 50 layers)
- no nucleus, packed with keratin
- layers continuously shed
keratinisation: enzymes remove cell organelles, leave mainly keratin = closely packed plates, tough, waterproof layer
- callouses from mechanical pressure
melanocytes: location/ features/ function
in basal layer, abundant cytoplasm, large irregular shape with projections extend in btw. keratinocytes
- produce melanin, skin pigment, blocks UV radiation from deeper skin layers
cytoplasm of epidermis:
contains ovoid granules, which produce melanin -> passes along cytoplasmic processes to basal and prickle cell layer keratinocytes
what gives skin colour?
melanin, carotene (temporary yellow), haemoglobin (pink/ red)
albinism:
lack of melanin in skin, eyes and hair, susceptible to damage from UV
Vitiligo:
autoimmune disease, degradation of melanin pigment, due to somatic cells not recognising
intraepidermal macrophages:
Langerhans cells
- important part of immune system, present in small no. on healthy skin
- ovoid nucleus, cytoplasm and cytoplasmic processes extending btw. keratinocytes
- mainly in spinosum
- in hypersensitivity reactions