Integumentary System Skin Epidermis

Skin Layers Stratified Squamous Epithelium Epidermis (upper) Dermis (lower)

Stratum Corneum Uppermost layer Thin, flat cells

Stratum Corneum

Dead and NO nuclei Continually shed

Stratum Corneum  Thick Cell membranes  Desmosomes present - strong

Stratum Corneum Keratinocytes – cells full of Keratin

Stratum Corneum Dry cells – Can act like a sponge – Prune look on soaking Latin for “horny layer”

Stratum Corneum

Provides barrier to – Water – Chemicals – Bacteria

Stratum Corneum Hyperkeratosis  Abnormal thickening of this layer  Dry and scaly skin

Stratum Corneum Hyperkeratosis

Epidermis Stratum Lucidum 2 nd Layer (3-4 layers) Prevents water loss

Stratum Lucidum Present in “Thick” skin – Hand Palms – Soles of feet

Stratum Lucidum Clear layer – Contains eleiden Protein becomes keratin Dead with NO nuclei

Stratum Lucidum

Stratum Granulosum 3 rd Layer (3-4 layers) Cells starting to die – Lysosomes – Degeneration of nuclei

Stratum Granulosum Granules present – Produce keratin – Keratinization begins here

Stratum Granulosum

Stratum Spinosum 4 th Layer (8-10 layers) Irregular-shaped cells

Stratum Spinosum Desmosomes – Connections between cells – “cell-to-cell adhesion”

Stratum Spinosum  If desmosomes are weakened, cells pull apart  As a result of exposure to chemicals, heat, or friction

Stratum Spinosum  Result: Blister  3. cross out

Stratum Spinosum Gives a “spiny” appearance

Stratum Spinosum

Heavy keratin production – Lots of RNA – Protein synthesis

Stratum Basale Lowest layer of epidermis

Stratum Basale Single layer – Simple Columnar looking cells – Looks like a line of fence posts

Stratum Basale

Mitosis occurs here Cells migrate to surface (35 days)

Stratum Basale Pressure over time – Increases mitosis – Results in callus

Epidermis – Layers Stratum Basale Stratum Spinosum Stratum Granulosum Stratum Lucidum Stratum Corneum