9.3 - The skin

• Biologie
• Middelbare school
• havo
• Leerjaar 2

9.3 The skin

Epidermis

Corneal layer - dead cells, filled with keratin.  Also known as stratum Corneum. 

Basal layer - living cells that keep on dividing

These are the 5 layers of the epidermis.  On the following slides we will go through each layer and identify the function.

What is the top layer of the epidermis called?

1. Stratum Lucidum
2. Stratum Germinativum
3. Stratum Spinosum
4. Stratum Corneum

Stratum Corneum

Stratum Lucidum

Stratum granulosum

Stratum spinosum

Stratum germinativum

The stratum corneum, also known as the horny layer.  The cells in the stratum corneum are filled with keratin, a protein which gives strength to the skin.  In this layer the cells are dead and flattened.

The cells of this layer form a waterproof covering for the skin and help to prevent  the penetration of bacteria.

The outer layer of dead cells is continually being shed, this process is known as desquamation.

The stratum lucidum, also known as the clear layer.  The cells in this clear layer are transparent which let light through.  

The stratum lucidum is very shallow in facial skin, but thick on the palms of the hands and soles of the feet and, is generally absent in hairy skin. 

The stratum granulosum, also known as the granular layer.  This layer consists of cells shaped like granules.  They are filled with keratin.

This layer prevents the absorption of harmful substances by the skin and helps maintain hydration of the lower layers. 

The stratum spinosum, also known as the prickle cell layer is the thickest layer of the epidermis.

It is known as the prickle cell layer because each of the rounded cells contained within it has short projections that make contact with the cell next to it, giving them a prickly appearance. 

It is in this layer that keratinisation occurs.

The stratum germinativum, also known as the basal cell layer is the deepest layer of the epidermis.

It is in this layer that mitosis occurs.

The cells appear round and contain a nucleus.

Mitosis - Cell reproduction

Nucleus - Control centre of the cell

Dermis

Blood vessel

Glands 

Muscles 

Hair

Receptors + nerves

Sensory receptors