Fundamentals of Anatomy and Physiology

The Integumentary System 117

Stratum corneum

Stratum lucidum^
Stratum granulosum
Epidermis

Stratum spinosum

Stratum germinativum

Papillary layer

Dermis

Reticular layer

Figure 6- 2 The epidermal and dermal layers of the skin.

The Stratum Germinativum
The stratum germinativum is the deepest and most
-important layer of the skin because it contains the only
cells of the epidermis that are capable of dividing by
mitosis. When new cells are formed they undergo
-morphologic and nuclear changes as they get pushed
upward by the dividing cells beneath them. Therefore, these
cells give rise to all the other upper layers of the epidermis.
The epidermis will regenerate itself only so long as the
stratum germinativum remains intact. Its basal layer, called
the stratum basale (STRAT-um BAY-sil), rests on the
basement membrane. It is this layer that produces new cells
via the process of cell division known as mitosis.

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The stratum germinativum also contains cells called
melanocytes (MEL-ah-no-sightz), which are
responsible- for producing skin color. Melanocytes are
irregularly shaped with long processes that extend between-
the other epithelial cells of this layer. They produce a
pigment called melanin (MEL-ah-nin), which