Chapter 5: The Epidermis

stratum basale

deepest epidermal layer made of a single row of cells that undergo rapid cell division

Merkel cells

function as touch receptors in association with sensory nerve endings located in stratum basale

Dendratic cells

in the stratum spinosum, are phagocytes that protect the skin and deeper tissues from pathogens.

Two structural features of keratinocytes that make epidermis stronger

manufacture keratin and linked together by demosomes

other cells of the epidermis

melanocytes, Dendratic (langerhans) cells, merkel cells

Kerationcyte life cycle

migration from the deepest strata to the stratum corneum takes a cell between 40-50 days to complete.

stradum lucidum

narrow layer of clear dead keratinocytes found only in thick skin.

Melanocytes

produce melanin found in stratum basale

layers of epidermis

stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, stratum corneum

stratum corneum

the most superficial layer of the epidermis consisting of dead cells that are sloughed off as the desmosomes are lost

Keratinocytes

The most abundant epidermal cells, they function mainly to produce keratin.

stratum granulosum

cells begin to die and become filled with keratin bundles or lipid-based substances

stratum spinosum

thickest layer, sits on top of the stratum basale so is still close to the blood supply. The cells in this layer are also metabolically and mitotically active

Keratin

tough fibrous protein that makes the epidermis more resistant to mechanical trauma.