Look down at your hands for a minute. Even though you can't see anything happening, your epidermis is hard at work. At the bottom of the epidermis, new skin cells are forming. When the cells are ready, they start moving toward the top of your epidermis. This trip takes about 2 weeks to a month. As newer cells continue to move up, older cells near the top die and rise to the surface of your skin.
What you see on your hands and everywhere else on your body are really dead skin cells. These old cells are tough and strong, just right for covering your body and protecting it. But they only stick around for a little while. Soon, they'll flake off. Though you can't see it happening, every minute of the day we lose about 30, to 40, dead skin cells off the surface of our skin. So just in the time it took you to read this far, you've probably lost about 40, cells.
That's almost 9 pounds 4 kilograms of cells every year! But don't think your skin might wear out someday. Your epidermis is always making new skin cells that rise to the top to replace the old ones. They make a substance called melanin say: MEL-uh-nun.
Melanin gives skin its color. The darker your skin is, the more melanin you have. When you go out into the sun , these cells make extra melanin to protect you from getting burned by the sun's ultraviolet, or UV, rays. That's why your skin gets tan if you spend a lot of time in the sun. But even though melanin is mighty, it can't shield you all by itself. You'll want to wear sunscreen and protective clothing, such as a hat, to prevent painful sunburns.
Protecting your skin now also can help prevent skin cancer when you get older. The next layer down is the dermis say: DUR-mis.
You can't see your dermis because it's hidden under your epidermis. One of the most important factors affecting this is skin hydration and environmental humidity. In healthy skin with normal hydration, medication can only penetrate the stratum corneum by passing through the tight, relatively dry, lipid barrier between cells. When skin hydration is increased or the normal skin barrier is impaired as a result of skin disease, excoriations, erosions, fissuring or prematurity, percutaneous absorption will be increased Rudy and Parham-Vetter, Melanocytes are found in the stratum basale and are scattered among the keratinocytes along the basement membrane at a ratio of one melanocyte to 10 basal cells.
They produce the pigment melanin, manufactured from tyrosine, which is an amino acid, packaged into cellular vesicles called melanosomes, and transported and delivered into the cytoplasm of the keratinocytes Graham-Brown and Bourke, The main function of melanin is to absorb ultraviolet UV radiation to protect us from its harmful effects. Skin colour is determined not by the number of melanocytes, but by the number and size of the melanosomes Gawkrodger, It is influenced by several pigments, including melanin, carotene and haemoglobin.
Melanin is transferred into the keratinocytes via a melanosome; the colour of the skin therefore depends of the amount of melanin produced by melanocytes in the stratum basale and taken up by keratinocytes. Skin colour is also influenced by exposure to UV radiation, genetic factors and hormonal influences Biga et al, Langerhans cells. These are antigen micro-organisms and foreign proteins -presenting cells found in the stratum spinosum. Merkel cells.
These cells are only present in very small numbers in the stratum basale. They are closely associated with terminal filaments of cutaneous nerves and seem to have a role in sensation, especially in areas of the body such as palms, soles and genitalia Gawkrodger, ; White and Butcher, This is a narrow, undulating, multi-layered structure lying between the epidermis and dermis, which supplies cohesion between the two layers Amirlak and Shahabi, ; Graham-Brown and Bourke, It is composed of two layers:.
The lamina lucida is the thinner layer and lies directly beneath the stratum basale. The thicker lamina densa is in direct contact with the underlying dermis. It undulates between the dermis and epidermis and is connected via rete ridges called dermal papillas, which contain capillary loops supplying the epidermis with nutrients and oxygen. This highly irregular junction greatly increases the surface area over which the exchange of oxygen, nutrients and waste products occurs between the dermis and the epidermis Amirlak and Shahabi, The dermis forms the inner layer of the skin and is much thicker than the epidermis mm White and Butcher, Situated between the basement membrane zone and the subcutaneous layer, the primary role of the dermis is to sustain and support the epidermis.
The main functions of the dermis are:. The network of interlacing connective tissue, which is its major component, is made up of collagen, in the main, with some elastin. Scattered within the dermis are several specialised cells mast cells and fibroblasts and structures blood vessels, lymphatics, sweat glands and nerves.
The epidermal appendages also lie within the dermis or subcutaneous layers, but connect with the surface of the skin Graham-Brown and Bourke, The papillary dermis is the thinner layer, consisting of loose connective tissue containing capillaries, elastic fibres and some collagen.
The reticular dermis consists of a thicker layer of dense connective tissue containing larger blood vessels, closely interlaced elastic fibres and thicker bundles of collagen White and Butcher, It also contains fibroblasts, mast cells, nerve endings, lymphatics and epidermal appendages. Skin cells live for about four to six weeks in young adults, and little longer than six weeks in older adults. Once a skin cell dies, it works its way to the outer layer of the epidermis, where it is shed.
Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Measurement of epidermis, dermis, and total skin thicknesses from six different body regions with a new ethical histometric technique. Turk J Plast Surg ; National Library of Medicine. Aging changes in skin.
Updated March 23, American Society of Clinical Oncology. Melanoma: introduction. January Your Privacy Rights. To change or withdraw your consent choices for VerywellHealth. At any time, you can update your settings through the "EU Privacy" link at the bottom of any page.
These choices will be signaled globally to our partners and will not affect browsing data. In addition, the soles of your feet and the palms of your hands are much thicker than skin on other areas of your body.
Squamous cells. 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.
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