what are the functions of the skin?
- protection
- containment
- thermoregulation
- immunological defense
- sensory abilities
- communication
- appendages (hair, nails, sebaceous glands, sweat glands)
how does the skin protect us?
resists abrasions and penetration, and blocks entry of foreign objects
containment function of the skin
prevents bodily fluid loss (keeps it in)
thermoregulation function of the skin
controls transfer of heat across the surface via heat retention and dissipation
communication function of skin
releases visual and pheromonal signals
layers of the skin starting from the top
epidermis:
- stratum corneum
- Stratum granulosum
- stratum spinosum
- stratum germinativum
basement membrane
dermis
properties of stratum germinativum
- columnar cells
- These are stem cells which differentiate and become cells of the layer on top
properties of stratum spinosum
- Polygonal cells
- These differentiate and become the cells of the layer on top
- Stuck together with desmosomes – no space, all stuck together
properties of stratum granulosum
- Flat cells packed with granules called keratohyalin granules
- Granules packed with keratin and lamellar bodies
properties of stratum corneum
No nucleus – are dead cells (from previous layer) that have released their contents (aka keratin and lamellar bodies)
what are the 3 general types of covering epithelia?
- simple
- stratified
- pseudostratified
types of simple epithelia (with description)
- columnar: taller than it is wide
- squamous: flatter
- cuboidal: all tall as it is wide
types of stratified epithelia
- squamous (keratinized and non keratinized)
- Transitional (e.g. bladder)
what are Pseudostratified columnar epithelial cells?
looks stratified because nuclei are on different layers, but is not (e.g. digestive tract)
