Information Courtesy of Nestle UK
A healthy skin is often a sign of a healthy diet and lifestyle but how can we make the most of our complexion? First a few basics:
The largest organ in the body, by weight and surface area, skin accounts for about 16% of an adult's body weight. Normally our skin acts as a barrier to the environment, however skin diseases and infections can compromise that barrier.
Our skin is also the way in which we interact with the outside world through the sensation of touch. It is a complex organ with many functions, including protection against water loss, wounds and the sun's ultraviolet (UV) rays; regulation of the body's temperature and metabolism, and the production of vitamin D when exposed to the sun.
Each square centimetre of skin is, on average, 3mm thick, containing 10 hair follicles, 100 sweat glands, and up to 2,500 sensory cells as well as 3 metres of lymphatic and blood capillaries, and 12 metres of nerve fibres.
Our skin is composed of several layers, each of which performs a specific function:
Hypodermis - The deepest and thickest layer, mainly composed of fat cells called adipocytes. These fat cells act as an energy reserve and fats are put back into the blood stream when needed. Since fat is a heat insulator, the hypodermis also helps to regulate the body's heat.
Dermis - The middle layer, made up of 80% water and a matrix of the proteins, elastin and collagen. It is the layer of tissue that supports the skin: collagen helps the skin resist strain, and elastin maintains elasticity. The dermis is able to provide energy and nutrition to the epidermis as well as play a role in thermoregulation and healing.
Epidermis - The visible layer, mostly impermeable to water and composed of connective tissue, blood vessels, nerve endings, hair follicles, sweat and oil glands. Thickness varies with age, gender and location on the body, e.g. epidermis on the underside of the forearm is about 5 cell-layers thick, whilst the sole of the foot might be 30 cell-layers thick.
The epidermis also consists of layers:
The stratum corneum or outer layer - Made of flattened epithelial (skin) cells in multiple layers called keratinized layers because of the build-up of the protein keratin, a strong protein specific to the skin, hair and nails. This layer of skin is, for the most part, dead, although still active, and is composed of cells that are almost pure protein.
The transitional layer - A transitional thin layer of cells most made up of keratin filaments.
The suprabasal layers - Comprised of 3 to 5 layers of flattened polygonal cells. Below them is a layer of cube-shaped cells that also contain bundles of keratin filaments.
The basal or cell-division layer - Just above the basement membrane and the dermis, this single layer of cells undergoes cell division to renew the upper layers of the epidermis. The human epidermis is renewed every 15-30 days. In some diseases this renewal process takes less time, for example in psoriasis the epidermis is renewed in about 7-10 days.
Keratinocytes - the most abundant cell type of the epidermis, producing keratin proteins that provide some of the rigidity of the outer layers of the skin. These also form the bulk of the material in hair follicles. Dandruff and hair are dead keratinocytes.
Fibroblasts - responsible for producing the dermis.
Melanocytes - cells in hair and the epidermis that produce the pigment melanin. Melanocytes are responsible for differences in skin and hair colour, and in the epidermis absorbs harmful UV light, protecting the skin's DNA from UV radiation damage.
Langerhans cells - immune cells (macrophages) found in the epidermis that protect the body from injury or illness by destroying invading organisms.
Merkel's Cells - most numerous in the palms of the hand and soles of the feet. Thought to be sensory mechanical receptors in the epidermis that respond to stimuli like pressure or touch.
Sebaceous glands - Embedded in the dermis over most of the body, but more concentrated in the scalp, face and forehead, these glands produce sebum, an oily substance containing waxes and lipids and may have weak antibacterial and antifungal properties. Sebaceous glands begin to function at puberty, when the male and female reproductive hormones kick in. If the normal, continuous flow of sebum is disrupted then acne can occur.
Sweat glands - Coiled, tubular glands that secrete sweat. Sweat is mostly water, sodium chloride (salt), urea, ammonia, and uric acid. Sweat gland ducts open at the skin's surface, similar to the opening of a hair follicle. Sweat is secreted for three main purposes: to moisten skin, to excrete waste, and to regulate body temperature through evaporation. Sweat glands receive messages from the nervous system which can alter the production of sweat, so sweating can be increased by being nervous or by eating spicy foods.
