Final answer:
The Stratum Spinosum is composed of eight to 10 layers of keratinocytes and contains immune cells called Langerhans cells. It is located above the stratum basale and is part of the skin's protective barrier formation.
Step-by-step explanation:
Stratum Spinosum Layers
The Stratum Spinosum is known for its spiny appearance due to the desmosomes that interlock the cells together, although this is an artifact from the staining process used to view these cells under a microscope. In its natural state, the stratum spinosum does not have this appearance.
This particular layer of the epidermis is composed of approximately eight to 10 layers of keratinocytes, which originate from cell division in the stratum basale.
Among the keratinocytes, Langerhans cells are present as part of the immune response, acting as macrophages to defend against pathogens and dying cells.
The stratum spinosum is situated above the stratum basale, and it is one of the layers that thickens significantly in areas of friction, contributing to the formation of calluses.
This layer is crucial for skin durability and is part of the process that leads to the production of the protective keratin layer found throughout the epidermis.
These keratinocytes also start gaining keratin in the stratum spinosum before they move up to the stratum granulosum, where they become fully keratinized.