The outermost layer is continuously shed is called the stratum corneum. Basal cells. Basal cells are found just under the squamous cells, at the base of the epidermis. Melanocytes are also found at the base of the epidermis and make melanin. This gives the skin its color. The dermis is held together by a protein called collagen. This layer gives skin flexibility and strength. The dermis also contains pain and touch receptors.
Helping us fight off bugs, allergens, toxins and carcinogens via the parts of our immune system that exist in our skin. Regulating our temperature by dilating and constricting our blood vessels near the skin surface, controlling the transfer of heat out of the body. Temperature is also regulated by evaporative cooling due to sweat production and by the insulating effect of erect hairs on the skin surface.
Heat loss is also affected by the insulating layer of subcutaneous fat. Protecting us from UV radiation by producing melanin. The production of Vitamin D , which helps prevent many diseases including osteoporosis, cancer, heart disease, obesity and neurological diseases. Beauty and physical attraction — the quality and condition of the skin greatly contributes to the perception of health, wellness, youth and beauty.
Normal healthy skin has many important roles and thus should be treated with care and respect. Many people only start focusing on the skin once there is an abnormality or at least a perceived problem. Common concerns include dryness, sensitivity, oiliness, congestion, wrinkles, sun damage and signs of ageing. Although these states are all within the spectrum of normal functional skin, they may be considered problematic if severe or undesirable.
Normal, healthy skin that is not exposed to excessive physical or environmental insults may not require any specific care or protection, but for those who want to optimise or improve their skin, some basic steps can make a big difference.
The key to skin care is consistency and routine, and it can take time to appreciate the changes. Switching and changing products and routines is usually counterproductive and will prevent you from seeing expected improvement in time. Festival of Social Science — Aberdeen, Aberdeenshire. People who do not produce melanin are called albinos.
They have pale skin and hair, and colourless irises. Hair, made of keratin, also helps to protect people from UV light as well as from extremes of temperature and trauma. Hirsutism hairiness varies among body areas and individuals. Each hair has a follicle in the dermis with its own nerve and blood supply Fig 2. The hypothalamus, which contains the temperature regulating centre, can orchestrate a number of changes within the skin in response to temperature changes.
Arteries and veins in the subcutaneous layer immediately beneath the dermis Fig 2 are linked to small arterioles and capillaries, which supply blood to the dermis. Blood flow can be varied by dilatation and constriction of these dermal blood vessels.
The blood carries heat with it to the skin surface. Heat is lost from the body in four ways:. Eccrine sweat glands assist in reducing body heat. There are about million of these glands Martini, and their distribution varies in different body areas. Sweat is composed of 99 per cent water, with sodium, urea, lactic acid and potassium making up the remaining one per cent.
We sweat an average of ml a day in the UK climate Marieb, , whether we are hot or not. But this can rise to 10 or more litres a day in very hot climates. Spicy foods and exercise also increase water loss through sweat.
The watery sweat drips off the skin, is absorbed into clothing or evaporates from exposed skin surfaces. In cold weather, blood supply to the skin is reduced Marieb, , as is sweat production. This conserves heat in the deeper organs, which are also insulated by the layers of subcutaneous tissue and fat. Tiny arrector pili muscles, around the shaft of the hair, contract and pull the hair vertically Martini, In animals with lots of hair, this results in the trapping of a layer of warm air around the body, and is an important means of insulation.
However, in humans it only results in goose pimples. Shivering occurs when the body becomes cold - this involuntary muscle action throughout the body is a metabolic process, which produces heat.
This ability to sense and provide information about contact of the skin with the outside world allows the brain to interpret and act upon the stimuli and helps to protect the body and avoid damage to it. There are nerve endings throughout the dermis but none in the epidermis.
Their distribution varies - for example, the fingertips and lips have many sensory receptors, giving them very fine sensory discrimination Hinchliff, The skin hairs also have a sensory nerve supply that senses when the hair is being touched.
Sebacious glands are outgrowths of hair follicles Fig 2 in the dermis. They secrete a lipid, sebum, to make the skin water-resistant. Sebum is bactericidal but if the glands become blocked, this results in a boil Martini, Very small amounts of carbon dioxide are excreted through the skin.
In addition to water, sweat excretes a number of waste products including sodium chloride and urea Marieb,
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