Introduction to Anatomy & Physiology of the Skin
The skin is the largest organ of our body. It is made up of three distinct layers:
The epidermis is made up of epithelial tissue and does not have a blood supply of its own. It is the layer of skin we can visually see. The epidermis renews itself every 15 to 30 days. It is made up of five layers:
Stratum Corneum (Horny Layer) – the outer layer, made up of scale like cells that are continuously shed.
Stratum Lucidium (Clear Layer) – made up of small transparent cells, usually only present in the soles of the feet and palms of the hands.
Stratum Granulosum (Granular Layer) – this layer of the epidermis is 1-3 layers thick. Keratin is produced in this layer.
Stratum Spinosum (Prickle Cell Layer) – this layer is 3-6 layers thick. The cells in this layer are constantly dividing.
Stratum Germinativum (Germinating Layer) – this single base layer of cells contains the melanocytes that produce the pigment melanin. Each of these cells has a distinct nuclei and the cells continuously divide through a process known as mitosis.
The dermis is the middle layer of the skin which is often referred to as our ‘true’ skin. The dermis is made up of connective tissues. It contains the blood and lymph supply which is provided by the lymph capillaries, arterioles and venules. It consists of two layers, the papillary layer and the reticular layer; the papillary (upper layer) contains thin collagen fibres, the reticular layer contains thicker collagen fibres and elastin fibres.
The Subcutaneous Layer
This is the deepest layer of the skin which is made up of connective tissues, adipose and areolar. Adipose (fatty) tissue, which is made up of adipocytes (fat cells), helps to protect our bodies, acting as a shock absorber, and also helps to insulate our bodies, keeping us warm.