Epidermal Structure

ANATOMY AND PHYSIOLOGY OF THE SKIN
In this module you will learn
The skin structure
The skin processes
The skin functions

THE LAYERS OF THE SKIN
The Epidermis
The Dermis
The subcutaneous layer

The epidermis is the top layer of the skin we can touch and see, it is made up of five distinct layers. The stratum germinativum, the stratum spinosum, the stratum granulosum, the stratum lucidum and the stratum corneum.
The dermis – This layer contains collagen, elastin, and glycosaminoglycans. It also contains the nerve endings, blood and lymph vessels, sensory nerve endings, sweat glands, hair follicle and sebaceous glands and erector pili muscle.
Hyper dermis/ subcutaneous layer-The subcutaneous layer is the fatty layer which protects the muscles, insulates heat loss, is an energy source and cushions the internal organs.

LAYERS OF THE EPIDERMIS

Horney layer / Stratum corneum

Clear layer / Stratum lucidum

Granular layer / Stratum Granulosum

Prickle Cell layer / Stratum spinosum

Basal layer / Stratum Germinativum

The epidermis is the outer layer of the skin and it is the skin that we can physically touch and see. This is made up of dead skin cells which are constantly being shed everyday.
It is classed as epithelial tissue that covers the outer surface of the body, these cells fit together and are known as STRATIFIED EPITELIUM.

The Stratum Germinativum or basal layer where cell mitosis takes place

The Stratum spinosum or prickle cell layer where cells differentiation begins

The Stratum Granulosum or Granular layer where the first signs of Keratinisation are clearly seen

The Stratum Lucidum or Clear layer where the Natural Moisture Factor is complete.

The Stratum Corneum or Horney layer which forms the multi layered, tough, cornified tissue of the surface.

Basal layer/ Stratum Germinative

• The cells still contain their nucleus
• It houses Melanocytes
• Cell division/cell mitosis take place
• At the Dermal Epidermal Junction (DEJ)

Melanocytes and Melanin

• The melanocytes cells are housed in the basal layer of the epidermis
• They produce a substance called melanin when exposed to UV radiation
• This is the skins natural protection from the UV rays

• Melanocytes are pigment forming cells
• 10% of cells in stratum Germinativum is a melanocyte
• Contain melanosomes within the cytoplasm –organelle producing melanin
• Octopus–like structure – melano-cytcdendrites
• Pass melanin to 30 – 36 skin cells
• Stimulated by UV rays
• Pigment then carried to surface epidermis

Prickle cell layer/ Stratum spinosum
• The desmosomes link the cells together
• The process of keratinisation starts to take place

Granular layer/Stratum Granulosum
• The process of keratinisation is well established
• The nucleus has now disappeared

Clear layer/Stratum Spinosum
• It is the thickest on the soles of the feet and palm of the hands
• No nucleus
• Protective Natural Moisture Factor is complete
• Prevents water loss from the deeper layers

Horney layer/ Stratum corneum
• The outer layer of the skin
• Packed so tightly they resemble fish scales under a microscope
• Protective barrier
• They are constantly being shed by the process of desquamation
• Kept moist by the natural moisture factor
• This layer can thicken immensely if the skin is not balanced in PH or exposed to harsh conditions