Integumentary
System
Skin Epidermis
Skin Layers
• Stratified Squamous
Epithelium
• Epidermis (upper)
• Dermis (lower)
Stratum Corneum
• Uppermost layer
• Thin, flat cells
Stratum Corneum
Stratum Corneum
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
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
• 2nd 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
• 3rd Layer (3-4 layers)
• Cells starting to die
– Lysosomes
– Degeneration of nuclei
Stratum Granulosum
• Granules present
– Produce keratin
– Keratinization begins
here
Stratum Granulosum
Stratum Granulosum
Stratum Spinosum
• 4th 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
Stratum Spinosum
Stratum Spinosum
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
Stratum Basale
Stratum Basale
• Mitosis occurs here
• Cells migrate to
surface (35 days)
Stratum Basale
• Pressure over time
– Increases mitosis
– Results in callus
Epidermis – Layers
Stratum Corneum
Stratum Lucidum
Stratum Granulosum
Stratum Spinosum
Stratum Basale