Anatomy and Physiology / Unit 3: The Integumentary System
3.2 Layers and Cells of the Epidermis
Notes
The epidermis renews itself continually. From deep to superficial the layers are:
- Stratum basale (germinativum): a single layer of dividing cells; contains melanocytes (make melanin) and tactile cells.
- Stratum spinosum: several layers of cells joined by desmosomes. Stratum granulosum: cells flatten and begin to die; keratin and waterproofing lipids are made.
- Stratum lucidum: a thin clear layer found only in thick skin (palms and soles).
- Stratum corneum: many layers of dead, keratinized cells that form the tough, waterproof outer barrier.
- Cells made in the basale take about 3 to 4 weeks to reach the surface.
- Key cells: keratinocytes (most abundant, make keratin), melanocytes, Langerhans cells (immune), Merkel cells (touch).
Practice
Which epidermal layer contains actively dividing cells?
New cells are produced by mitosis in the deepest layer, the stratum basale.
The outermost epidermal layer consists of:
The stratum corneum is dead keratinized cells that resist abrasion and water loss.
Which cell type produces the pigment that protects DNA from ultraviolet radiation?
Melanocytes make melanin, which is transferred to keratinocytes and shields their nuclei.
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