#Coloring page layers of the skin skin#
In the thick skin on the soles of the feet and palms of the hands the stratum lucidum is a thin, transparent layer of dead keratinocytes lying superficial to the stratum granulosum. Beyond the stratum granulosum the keratinocytes are cut off from their blood supply and begin to die, resulting in layers of dead keratinocytes on the body’s exterior.Keratinocytes in the stratum granulosum also secrete lamellar granules, a waterproof substance that prevents water from leaking out of the body’s tissues or leaking into the body from the external environment.
The granular appearance of keratinocytes is due to keratin and other chemicals accumulating inside the cells. The next layer, the stratum granulosum, is a thin layer featuring granular keratinocytes that have been pushed out of the stratum spinosum.Desmosomes hold the cells together tightly while keratin fills the cells and gives the skin its strength and water resistance. In the stratum spinosum, these keratinocytes begin to fill with keratin and form spiny connections between cells known as desmosomes. Young keratinocytes are pushed into this layer from the reproduction of stem cells in the stratum basale. Superficial to the stratum basale is a thicker layer of epidermis known as the stratum spinosum, or spiny layer.Special touch sensitive cells known as Merkel cells are also present in the stratum basale to detect the shape and texture of objects touched by the skin. Melanocytes found in this layer produce the pigment melanin to give the skin its coloration and protect the body from ultraviolet radiation. If this layer is destroyed in a particular region, the epidermis cannot regrow and is replaced by scar tissue. The deepest layer of the epidermis is the stratum basale (stratum germinativum), a layer of stem cells that produce all of the keratinocytes, or skin cells, in the epidermis.
The epidermis is made of four to five layers of epithelial tissue that constantly grows from the inside out and replaces most of its cells every few weeks.
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