Epidermis

The epidermis is divided into five main layers (4 layers in some texts).

These layers are avascular but the deeper layers are nourished by the tissue fluid from the vascular papillae. Starting from the deepest layer of the epidermis, the stratum germinativum or germinative layer (stratum = layer), is where the cells keep multiplying continuously to provide the cells that are lost from the surface of the epidermis.

The cells from the germinative layer move upwards into the layer above termed the prickle or spinous layer (stratum spinosum) named for the bridges between the cells.

These two layers are often called the malphigian layer. They are responsible for proliferation and initiation of the keratinization process. (Kerat-, means hard)

Granular Layer

The next layer is the stratum granulosum or granular layer where the cells contain granules which are involved in the formation of soft keratin.

As the number and size of these granules increases up the layer, the nucleii become pale and indistinct. It is in this layer that cells of the epidermis die.

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