Topic Set 3: Epidermal Layers (Basale to Corneum)

What are the 5 layers of the epidermis from deep to superficial?

Stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum

What is the structure of the stratum basale?

Single layer of cuboidal cells

What attaches stratum basale to the basement membrane?

Hemidesmosomes

What is the function of the stratum basale?

Mitosis to produce skin cells, keratin, and vitamin D precursors

What two special cell types are in the stratum basale?

Melanocytes and Merkel's discs

What is the sensitivity of a Merkel's disc?

Very sensitive touch receptor

What is the structure of the stratum spinosum?

8–10 cell layers

How are cells in the stratum spinosum connected to neighboring cells?

Extensive desmosomes

What are the functions of the stratum spinosum?

Produce vitamin D, produce keratin, and occasional mitosis

What structures form inside the stratum spinosum?

Lipid-filled lamellar bodies

What is the structure of the stratum granulosum?

3–5 cell layers

What cells are found in the stratum granulosum?

Langerhans cells

What are keratohyaline granules?

Granules involved in keratin production

What do lamellar bodies release in the stratum granulosum?

Lipids at the cell membrane surface

Why do cells undergo apoptosis in the stratum granulosum?

Too far from the dermal blood supply

What is the structure of the stratum lucidum?

4–6 layers of clear, dead cells full of keratin

Where is the stratum lucidum found?

Only in thick skin

What is the structure of the stratum corneum?

25–30 layers of dead, cornified cells full of keratin

Why do cells shed from the stratum corneum?

Loss of desmosomes

What type of keratin is found in skin cells?

Soft keratin

What is dandruff?

Excessive shedding of stratum corneum on the scalp

What is a callus?

Abnormal thickening of stratum corneum from repeated pressure or friction