Skin Structure
Skin Structure
When talking about ageing, it helps to first understand the structure of the skin. Your skin is the largest of all your body organs and consists of:
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64%-72% water (2% of the total water content of the body)
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22% protein
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13% fat
There are also trace elements present such as sodium, calcium, magnesium, potassium, phosphorus, sulphur, iron, copper, zinc, chlorine, and iodine.
The skin is composed of three tissue layers:
The epidermis is the outermost layer; it is paper-thin (0.1 mm) consisting of cells and lipids—or less elegantly—fat, which prevents the evaporation of water and protects against damage from outside influences. The barrier of the skin also acts to prevent infections from entering the body. Sweat and sebum contain substances that inhibit the growth of bacteria on the skin surface.
The epidermis is the only skin layer that renews itself completely in a regular rhythm (every 28-31 days) as a result of cell division in the subcutis. The cells change continually on their way to the surface, forming different layers until they are finally sloughed off from the horny layer (known as the stratum corneum). An adult sheds approximately 10 grammes of skin a day.
The dermis is below the epidermis; it is a dense, flexible layer of connective tissue. The connective tissue consists of tissue cells and collagen fibres (98% collagen and 2% elastin), which give the skin its firmness and resilience. The dermis is important for metabolic processes and temperature regulation.
Nerves are also located in the dermis, which carry messages about heat, cold, pressure and pain to the central nervous system. It's this layer that supports the skin's structure, containing collagen, elastin, hyaluronic acid (HA), and fibres.
The subcutis (subcutaneous fatty tissue) is the deepest layer; it is a thick tissue layer composed of loose connective tissue. Embedded in this network structure are groups of fat cells, held together by collagen fibres. Fatty tissue acts as an energy reservoir, protective padding, and heat insulation. The subcutis connects the skin to deeper tissue layers.
