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ABOUT THE SKIN AND HOW TO LOOK AFTER IT

Skin is a remarkable organ of the body which is able to perform various vital functions. It can mould to different shapes, stretch and harden, but can also feel a delicate touch, pain, pressure, hot and cold, and is an effective communicator between the outside environment and the brain.

Skin makes up to 12-15% of an adult's body weight. Each square centimeter has 6 million cells, 5,000 sensory points, 100 sweat glands and 15 sebaceous glands. It consists of 3 layers: the epidermis (the outer layer), the dermis ('true skin') and the subcutaneous (fat) layer.

Skin is constantly being regenerated. A skin cell starts its life at the lower layer of the skin (the basal layer of the dermis), which is supplied with blood vessels and nerve ending. The cell migrates upward for about two weeks until it reaches the bottom portion of the epidermis, which is the outermost skin layer. The epidermis is not supplied with blood vessels, but has nerve endings. Foe another 2 weeks, the cell undergoes a series of changes in the epidermis, gradually flattening out and moving toward the surface. Then it dies and is shed. Below is a detailed diagram of the skin structure:

Skin Structure

Epidermis

The main function of the epidermis is to form a tough barrier against the outside world, while the dermis is a soft, thick cushion of connective tissue that lies directly below the epidermis and largely determines the way our skin looks. Both layers keep repairing and renewing themselves throughout or life, but the dermis does it more slowly than the epidermis. Under the dermis is a layer of fat cells, which is know as adipose tissue (or subcutaneous fat layer). It provides insulation and protective padding for the body. It also provides an emergency energy supply.

The epidermis consists of 5 layers:

  • Basal layer (Stratum germinativum) - this is the bottom layer of the skin. The cells of this layer constantly been reproduced, since they contain a nucleus, or seed. As the cells reproduce, the layers get constantly pushed up into the next layer.

  • The prickle cell layer (Stratum spinosum) - called this way because the cells have spines which prevent bacteria entering the cells and moisture being lost. These cells also have a nucleus and therefore reproduce.

  • Granular layer (Stratum granulosum) - the prickle cells lose their spines and become flatter. The nucleus dies, and protein is formed called keratin. This protein prevents moisture loss and is found in skin, nails and hair.

  • Clear layer (Stratum lucidum) - this layer is for cushioning and protection and is found only on the palms of the hands and soles of the feet.

  • Horny (cornified) layer (Stratum corneum) - the cells here are dead and ready to be shed (desquamation). This process speeds up as we age.

Dermis

The dermis is the layer responsible for the skin's structural integrity, elasticity and resilience. Wrinkles develop in the dermis. Therefore, an anti-wrinkle treatment has a chance to succeed only if it can reach the dermis. Typical collagen and elastin creams, for example, never reach the dermis because collagen and elastin molecules are too large to penetrate the epidermis. Hence, contrary to what some manufacturers of such creams might claim, these creams have little effect on skin wrinkles.

The dermis is the middle layer of the skin located between the epidermis and subcutaneous tissue. It is the thickest of the skin layers and comprises a tight, sturdy mesh of collagen and elastin fibers. Both collagen and elastin are critically important skin proteins: collagen is responsible for the structural support and elastin for the resilience of the skin. The key type of cells in the dermis is fibroblasts, which synthesize collagen, elastin and other structural molecules. The proper function of fibroblasts is highly important for overall skin health.The dermis also contains capillaries (tiny blood vessels) and lymph nodes which produce immune cells. Blood capillaries are responsible for bringing oxygen and nutrients to the skin and removing carbon dioxide and products of cell metabolism (what we call waste matter). Lymph nodes are engaged in protecting the skin from invading microorganisms.Finally, the dermis contains sebaceous glands, sweat glands, hair follicles and a small mumber of nerve and muscle cells. Sebaceous glands, based around hair follicles, produce sebum, an oily protective substance that lubricates the skin and hair and provides protection by forming an acid mantle when mixed with sweat. When sebaceous gland produce too little sebum, as is common in older people, the skin becomes excessively dry and more prone to wrinkling. Too much of sebum, as is common in teenagers, often leads to acne.

The dermis is thicker than the epidermis, but has fewer cells. It consists mainly of connective tissue which is made up of fibers of the proteins collagen and elastin and a non-fibrous gelatin-like material called ground substance or extracellular matrix.

Subcutaneous tissue

Subcutaneous tissue is the deepest layer of the skin located under the dermis and consisting mainly of fat cells. It acts as a shock absorber and heat insulator, protecting underlying tissues from cold and trauma. The loss of subcutaneous tissue in later years, leads to facial sag and makes wrinkles more visible. To counteract it, a cosmetic procedure where fat is taken from elsewhere in the body and injected into facial areas, is common these days.

Skin Functions

There are 6 skin functions:

  • Sensation - the nerve endings in the skin identify touch, heat, cold, pain and light pressure.

  • Heat regulation - the skin helps regulate the body temperature by sweating to cool the body down when it overheats and shivering creating 'goose bumps' when it is cold. Shivering closes the pores. The tiny hair that stands on end traps warm air and thus helps keep the body warm.

  • Absorption - absorption of ultraviolet rays from the sun helps to form vitamin D in the body, which is vital for bone formation. Some creams, essential oils and medicines (e.g. HRT, anti-smoking patches) can also be absorbed through the skin into the blood stream.

  • Protection - the skin protects the body from ultraviolet light - too much of it is harmful to the body - by producing a pigment called melanin. It also protects us from the invasion of bacteria and germs by forming an acid mantle (formed by the skin sebum and sweat). This barrier also prevents moisture loss.

  • Excretion - Waste products and toxins are eliminated from the body through the sweat glands. It is a very important function which helps to keep the body 'clean' from the inside.

  • Secretion - sebum and sweat are secreted onto the skin surface. The sebum keeps the skin lubricated and soft, and the sweat combines with the sebum to form an acid mantle which creates the right ρH balance for the skin to fight off infection.