What type of cells primarily make up the Spinosum layer of the epidermis?

The Spinosum layer of the epidermis is primarily composed of prickle cells, also known as spinous cells. These cells are located above the Basale layer and play a crucial role in the strength and flexibility of the skin. Prickle cells are characterized by their spiny appearance due to desmosomal connections that link adjacent cells, providing structural support and enabling communication between cells.

In this layer, the cells begin the process of keratinization, where they start to produce keratin, the protein that will eventually provide waterproofing and protection to the skin. The presence of prickle cells is essential for the overall integrity of the epidermis, as they help to form a barrier against environmental damage.

While basal cells are located in the Basale layer and are primarily responsible for cell proliferation, and keratinocytes are the predominant cell type in the epidermis as a whole, it is specifically the prickle cells that define the Spinosum layer. Squamous cells can refer to flattened cells found in various layers, but in this context, the term "prickle cells" most accurately describes the unique morphology and function of the cells in the Spinosum layer.