Layer of Epidermis

Question 1

The outer most layer consisting of 20-30 layer of dead, scalelike keratinocytes. They are constantly being exfoliated and replaced by the division of the deeper cells.

Answer 1

Stratum corneum (horny layer)

Question 2

Present only in thick skin. A very thin transparent band of flattened, dead keratinocytes with indistinct boundaries.

Answer 2

Stratum lucidum (clear layer)

Question 3

A thin layer named for the abundant granules its cells contain. These granules are (1) lamellar granules, which contain a waterproofing glycolipid that is secreted into the extracellular space; and (2) keratohyaline granules, which help to form keratin in the more superficial layers. At the upper border of this layer, the cells are beginning to die.

Answer 3

Stratum granulosum (granular layer)

Question 4

Several layers of cells that contain thick, weblike bundles of intermediate filaments made of pre-keratin protein. The cells in this layer appear spiky because when the tissue is prepared, the cells shrink, but their desmosomes hold tight to adjacent cells. Cells in this layer and the basal layer are the only ones to receive adequate nourishment from diffusion of nutrients from the dermis.

Answer 4

Stratum spinosum (spiny layer)

Question 5

A single row of cells immediately about the dermis. Its cells are constantly undergoing mitosis to form new cells, hence its alternative name, stratum germinativum. Some 10-25% of the cells in this layer are melanocytes, which thread their process through this and adjacent layers of keratinocytes. occasional tactile epithelial cells are also present in this layer.

Answer 5

Stratum basale (basal layer)