Skin Flashcards
Main Functions of skin
Protection, sensory, thermoregulatory, metabolic and absorptive
Protective function explained
provides a physical barrier against pathogens and friction. Pathogens that do get in alert antigen presenting cells in the skin which initiate an immune response. Melanin protects nuclei from UV radiation. Prevents excessive water loss.
Sensory function explained
contains many sensory receptors and mechanoreceptors
thermoregulatory function explained
Fatty layer- helps maintain heat, hair follicles, sweat production
metabolic function explained
cells of skin synthesise vitamin D needed in calcium metabolism and bone formation
Absorptive function
skin patches can be placed, containing nicotine, hormone replacements, steroids etc.
3 main layers of skin
epidermis, dermis and hypodermis
What type of epithelium is the epidermis?
Stratified squamous
4 main epidermal layers
Basal layer (stratum basale), spinous layer (stratum spinosum), granular layer (stratum granulosum) and stratum corneum
Stratum Basale location
between the dermis and stratum spinosum. Bound to the basal lamina via hemidesmosomes
Stratum Basale cell type
simple cuboidal or columnar
How is the stratum basale characterised?
Intense mitotic activity. Contains progenitor cells for the epidermal layers and basal stem cells for the keratinocytes.
What sorts of keratin is expressed?
cytoskeletal keratins are 10 nm in diameter.
How often are the stratum basale epithelial cells renewed?
25-30 days
What is normally the thickest layer in the epidermis?
Stratum spinosum
What are the prickles on the stratum spinosum cells?
Tonofibrils assembled from keratin fibre bundles that terminate at numerous desmosomes, holding the cell layers together.
Where will epidermis have a larger stratum spinosum?
Skin where there is a lot of friction, such as the foot sole
What type of cells are in the basale granulosum?
flattened
What process are they undergoing?
Terminal differentiation process of keratinisation
What is the cytoplasm of the basale granulosum cells filled with?
basophilic keratohyaline granules
What are keratohyaline granules?
dense, non- membranous bound masses of filaggrub and other proteins associated with keratin
Keratohyaline granule functions
cross link proteins together in a big mass, forming a cornfield layer
What else occurs in the basle granulosum?
small keratinosomes are released, filled with lipids producing water proofing
What cells are present in the stratum corneum?
15-20 layers of squamous cells, that have been squashed and migrated from the stratum basale’s cuboidal cells