Figure 2-1. Structure of the skin and underlying subcutaneous layer.
(a) Stratum basale. Cells continually multiply and push upward toward
(b) Stratum spinosum. Eight to ten rows of polyhedral (many-sided)
cells which fit closely together make up this layer of epidermis. New cells germinate in
(c) Stratum granulosum. Three to five rows of flattened cells
containing keratohyalin, a substance which will finally become keratin, make up this
layer of epidermis. The nuclei of cells are in various stages of degeneration-breaking
down and dying.
(d) Stratum lucidum. This layer is thicker on the palms of the hands
and the soles of the feet. The layer consists of several rows of clear, flat, dead cells
which contain droplets of a clear substance called eleidin. Eleidin eventually becomes
(e) Stratum corneum. Twenty-five to thirty rows of flat, dead cells
which are completely filled with keratin make up this layer. These cells are shed and
replaced continuously so that roughly every twenty-eight days, this layer is new. It is
this layer with its water-proofing protein keratin that protects the body against heat and
light waves, water, bacteria, and many chemicals.