Filling in wrinkles safely. Food and Drug Administration. Kermott CA, et al. Sunscreen: How to protect your skin from the sun. Sunscreen FAQs. The American Academy of Dermatology. Krutmann J, et al.
The skin aging exposome. Journal of Dermatological Science. Topical tretinoin topical all-trans retinoic acid : Patient drug information. Goldberg DJ. Ablative laser resurfacing for skin rejuvenation. Riggin EA. Decision Support System. Mayo Clinic, Rochester, Minn. July 26, Chemical peels: FAQS.
Gibson LE expert opinion. Mayo Clinic. Edmonson KG, et al. Laser skin resurfacing: Cosmetic and medical applications. In: Fitzpatrick's Dermatology. McGraw-Hill Education; Related Deep, coarse wrinkles Wrinkle creams Wrinkles. Mayo Clinic Press Check out these best-sellers and special offers on books and newsletters from Mayo Clinic.
This is the last article in our series on the anatomy and physiology of ageing. Nursing Times [online]; 12, Authors: Yamni Nigam is associate professor in biomedical science; John Knight is senior lecturer in biomedical science; both at the College of Human Health and Science, Swansea University.
The fact that it covers the entire body means the skin is the most obvious place to observe signs of ageing. The skin consists of two main parts: the epidermis and the dermis. The epidermis is the outside layer and protects the underlying layers from the environment. It hosts cells that produce keratin, a substance that makes the skin waterproof and stronger, and cells that contain melanin, a photo-protective pigment that gives skin its colour.
Although there is no blood supply in the epidermis, there are cells that afford the body immunity against bacteria and other invading organisms. The second layer or dermis, the thickest layer of skin, contains cells that give skin its strength, support and flexibility. Sensory receptors in the dermis allow the body to experience pressure, pain and temperature, while small blood vessels provide the skin with nutrients and remove its waste products. Sebaceous glands — present all over the body except on the palms of the hands and the soles of the feet — produce oil that keeps the skin hydrated, softens hair and helps kill bacteria in the pores.
The dermis also hosts the sweat glands and hair follicles. Below these two main layers is an innermost layer of subcutaneous tissue, the hypodermis. This anchors the skin to the fascia the underlying connective tissues that wrap around skeletal muscles and is therefore known as the superficial fascia.
The hypodermis consists mainly of fat cells that insulate the body and helps it to conserve heat. Blood flow in the dermis helps the body adjust to cold and heat. Sweat glands produce about ml of sweat a day, providing an important cooling mechanism. In hot weather, the nervous system stimulates the dermal blood vessels to dilate and sweat glands can increase their production to up to 12L a day Marieb and Hoehn, The evaporation of sweat cools the body and prevents it from overheating.
In cold weather, the dermal blood vessels constrict, warm blood flow bypasses the skin, the skin cools down further and this slows down heat loss from the body. The skin acts as a storage facility for lipids and water.
When it is hit by sunlight, modified cholesterol molecules are converted to a vitamin D precursor, which is transported to other body areas to be made into vitamin D essential for calcium absorption from the gut.
Skin cells also make collagenases; these are enzymes that support the natural turnover of collagen. The skin has a variety of nerve endings that feel touch, pressure, vibration, warmth, cold and pain, allowing the body to receive sensory stimulation from the surrounding environment. With its stratum corneum multiple layers of dead, flat cells and glycolipids and hard keratinised cells, the skin forms a continuous physical barrier.
It also provides chemical barriers:. Skin ages intrinsically chronologically from within and extrinsically due to external factors. Intrinsic skin ageing results from the passage of time and is mainly due to the action of reactive oxygen species ROS Box 1 Naidoo and Birch-Machin, It occurs within the skin itself due to reductions in dermal mast cells, fibroblasts and collagen production, and a flattening of the junction between the epidermis and dermis.
Intrinsically aged skin is unblemished, smooth, pale, dry and less elastic with fine wrinkles Landau, Such factors have been shown to stimulate the production of ROS and generate oxidative stress Valacchi et al, Actinic exposure affects the epidermis, causing irreparable damage to cellular DNA, and induces the generation of ROS. Less than 30 minutes after UV irradiation, the amount of hydrogen peroxide — a potent ROS — has been shown to more than double in human skin Rigel et al, UV exposure also disrupts collagen synthesis, leading to acute collagen loss Rinnerthaler et al, Exposure to UV radiation increases skin pigmentation and stimulates melanocyte proliferation.
Melanin helps protect against the cumulative damaging effects of UV radiation, which explains why the rates of skin cancer are much higher in Caucasians than in black people and why basal cell carcinomas occur almost exclusively in the sun-exposed skin of light-skinned people Tobin, Extrinsically aged skin is characterised by coarse and deep wrinkling, rough texture, telangiectasia spider veins , irregular or mottled pigmentation, a sallow or yellow complexion and a loss of elasticity Tobin, The severity of extrinsic ageing depends on skin type — fairer skin is affected more than darker skin.
The epidermis is formed of protective keratinised squamous epithelial tissue, with an outer barrier of dead cells stratum corneum. Underneath are several layers of epidermal cells, ending in a basal layer of rapidly dividing cells located next to the basement membrane and dermis. Keratinocytes cells producing keratin and melanocytes cells producing melanin are found in the epidermis.
With age, there is a substantial loss of melanocytes and Langerhans cells Yaar and Gilchrest, Having no blood supply, the epidermis gains its nutrition through contact with the dermis. A major cutaneous change in intrinsic skin ageing is a reduction in the surface contact between the epidermis and dermis.
There is a loss of rete ridges epithelial extensions that project into the underlying connective tissue , which negatively affects the capillary-rich dermal papillae, resulting in a reduced supply of nutrients, metabolites and oxygen to the epidermis Tobin, The reduced contact between dermis and epidermis also results in less resistance to shearing forces. The stratum corneum has a barrier function and keeps the skin from drying out; although it does not become thinner with age, it is not replaced as quickly, so skin is increasingly rough and dry.
Extreme skin dryness xerosis can be seen in ageing skin, and this brings about an increased susceptibility to irritant dermatitis Tobin, As mitosis in the basal layer of the epidermis is slowed down, healing takes more time. With advancing age, there is a reduction in the hormones and chemical signals that are important for skin growth and repair, as well as a decline in the receptors that detect them; as an example, the number of vitamin D receptors in epidermal keratinocytes declines with age.
The dermis contains blood capillaries that are important for providing oxygen and nourishment to all skin cells. It comprises an extracellular matrix containing a sturdy mesh of collagen and elastin fibres, which give the skin its strength, elasticity and resilience. Key cells in the dermis are:. In addition, collagen itself changes from well-organised bundles of fibres in young skin to fragmented and dis-organised fibres in older skin; it also loses its interwoven extensions with elastin fibres, which in youth enable the skin to regain its shape after deformation Graham-Brown, Fibroblast activity decreases with age: these cells shrivel and have fewer epidermal growth factor receptors.
There is an associated drop in collagen synthesis, an atrophy of collagen bundles and an increase in the levels of metalloproteinases and enzymes that degrade collagen. As a consequence, collagen is of poor quality and wound healing is impaired.
As collagen fibres decrease in number, rupture, cross-link and stiffen, their capacity to bind water diminishes and the skin loses elasticity and becomes wrinkled. Wrinkles appear to be due not so much to the degeneration of elastin fibres, as previously thought, but to a decreased water-holding power of collagen and mucopolysaccharides Richards and Edwards, Skin ageing is associated with a decrease in cutaneous perfusion and reduced vascularity, mainly in the superficial papillary part of the dermis.
There is a drastic reduction in the number of dermal blood vessels accompanied by a shortening of capillary loops in the dermal papillae.
This results in skin pallor, depleted nutrient exchange and impaired thermoregulation Baumann, ; Waller and Maibach, The hypodermis consists mainly of fat, and acts as an insulator and shock absorber.
With age, there is a loss of subcutaneous fat and the skin becomes thinner and less resistant to trauma. The reduced volume of subcutaneous fat means the role of the hypodermis in limiting conductive heat loss is impaired.
The distribution of subcutaneous fat changes too: it decreases in parts of the face and hands but increases in the thighs and abdomen. The effects of gravity over time do play a subtle role in sagging skin. On top of that, muscle weakness in the facial muscles can worsen sagging skin, although this is not as much of a concern as changes in the skin and facial volume.
Now that we know what causes sagging skin, how can we slow down its progression? Fortunately, many aesthetic skin treatments work by stimulating the production of collagen. However, properly using these powerful devices requires considerable skill. Worse, these treatments can pose a safety risk in the wrong hands. Your best bet is to choose an expert in skin tightening treatments, like the team at Hillelson-Whipple Clinic. Our experienced team has performed thousands of Thermage treatments and are known for their excellent results in this procedure.
If sagging skin has got you feeling down, call Hillelson-Whipple Clinic in Richmond, VA, to schedule your consultation today at Terry L. Whipple, M.
0コメント