Page 193 - Fundamentals of anatomy physiology

Spotlight Figure 5–3
The Epidermis

BASIC ORGANIZATION OF THE EPIDERMIS Stratum
corneum
The epidermis consists of stratified squamous epithelium.
Basement
It is separated from the dermis by a basement membrane. membrane

The stratum basale and the underlying dermis interlock, Dermis

strengthening the bond

between the two. The Epidermis

epidermis forms epidermal Basement

ridges, which extend into membrane

the dermis and are Epidermal ridge

adjacent to dermal Dermal Thin skin LM ϫ 200

papillae that project into papilla Thin skin contains four
layers of keratinocytes, and
the epidermis. Dermis is about as thick as the wall
of a plastic sandwich bag
LAYERS OF THE EPIDERMIS (about 0.08 mm).

The layers of the epidermis are best shown in a sectional view of thick skin. Thick skin contains
a fifth layer, the stratum lucidum. Because thick skin also has a much thicker superficial layer
(the stratum corneum), it is about as thick as a standard paper towel (about 0.5 mm).

Surface Epidermis Characteristics
Stratum corneum
Basement • Multiple layers of flattened, dead, interlocking
membrane keratinocytes

• Water resistant but not waterproof
• Permits slow water loss by insensible

perspiration

Stratum Stratum lucidum • Appears as a glassy layer in thick skin only
corneum

Stratum granulosum • Keratinocytes produce keratohyalin and keratin
• Keratin fibers develop as cells become thinner

and flatter
• Gradually the plasma membranes thicken, the

organelles disintegrate, and the cells die

Stratum Stratum spinosum • Keratinocytes are bound together by
lucidum desmosomes

Stratum basale • Deepest, basal layer
• Attachment to basement membrane
Dermal • Contains basal cells (stem cells),
papilla
melanocytes, and tactile cells (Merkel cells)
Epidermal
ridge Thick skin LM ϫ 200 Dermis

EPIDERMAL RIDGES OF THICK SKIN Pores of sweat
gland ducts
Fingerprints reveal the pattern of epidermal ridges.
This scanning electron micrograph shows the Epidermal
ridges on a fingertip. ridge

180 Thick skin SEM ϫ 20