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What is the Epidermis?
the layer that responds to pressure or injury to the skin
What layer is the Epidermis?
upper layer (top layer on top of dermis)
What is the Epidermis composed of?
stratified keratinized squamous epithelium
What are the 4 cells of the Epidermis?
What is Keratinocytes?
produces keratin. They arise at the lower part of epidermis & are pushed up as new ones are created. As they reach the top they flatten out. At this time they are filled with keratin and have died. We get a new epidermis every month
What are Melanocytes?
make melanin (dark pigment) which is transferred to the keratinocytes. The melanin protects DNA from UV ray damage. Melanin production is increased as a result of UV exposure. Skin tone is a result of the rate at which melanin is destroyed by lysosymes.
What does Melanin protect?
Melanin protects DNA from UV Ray Damage
What is Merkel Cells?
associated with a sensory nerve ending - it is a touch receptor
What are Langerhans cells?
star shaped cells that form part of the immune system & use receptor mediated endocytosis to engulf foreign substances.
What is another term for layer?
What varies in the number of strata in the epidermis?
the thickness of skin
What does the Epidermis protect?
Epidermis is the section of skin that protects and waterproofs the body
What is Stratum basale?
a basal layer that gives rise to newly formed keratinocytes & melanocytes.
What is the stratum basal layer attached to and looks like?
statum basal is attached to underlying dermis & is a single row of stem cells with a high rate of mitosis. The high mitotic rate pushes the cells into the next layer.
What does the high mitotic rate do to the cells?
pushes the cells into the next layer
What is the stratum spinosum?
a spiny layer of mature keratinocytes that have formed tonofilaments (prekeratin intermediate filaments)
What does the Stratum Spinosum look like?
several layers thick and also has langerhans cells.
What is stratum granulosum?
a granulayer where keratinocytes flatten & plasma membrane thickens
What does the stratum granulosum look like?
4-5 layers of flat keranocytes with the cells changing becoming waterproof and keratinized.
What is the stratum lucidum?
a clear layer with cells that die from getting no nutrients
Where is the stratum lucidum found and what does it look like?
Stratum Lucidum is found in thick skin and appears as a clear band under the microscope.
What is the stratum corneum?
horny layer that protects against abrasions & entry of foreign substances. The cells are dead flat keratinocytes filled with keratin.
What does the stratum corneum look like and where is it found?
Stratum Corneum is many layers found in thick or thin skin. It is the outermost layer (the surface of your body)
The layers at the surface of your body, what are the cells?
at this point the cells are dead, have no organelles, & are filled with keratin & hold waterproofing glycolipids in between cells.