In order to understand contemporary psychology, it is important to look back at the origins and influences on this science. Courses on the history of psychology generally begin with the subject's ancient philosophical origins and explore the contributions of major thinkers up through the modern-day.
Spinous cells, or prickle cells, are keratin producing epidermal cells owing their prickly appearance to their numerous intracellular connections. They make up the stratum spinosum (prickly layer) of the epidermis and provide a continuous net-like layer of protection for underlying tissue.hey are pushed upward into the stratum spinosum by the continuous formation of new cells in the basal layer. They reach the outmost layer of the skin as flattened dead flaking skin cells we shed daily. The journey from origin to shed takes 25 to 45 days.
The fourth layer in the epidermis is called the stratum lucidum, or the clear layer. This layer is present only in the fingertips, palms, and soles of the feet. It is 3-5 layers of extremely flattened cells. The fifth layer, or horny layer, is called the stratum corneum. This is the top, outermost layer of the epidermis and is 25-30 layers of flattened, dead keratinocytes. This layer is the real protective layer of the skin.