Biology of aging skin
The skin which is the largest organ covers the entire external surface of the human body and is the principal site of interaction with the surrounding world. It serves as a protective barrier that prevents internal tissues from exposure to trauma, ultraviolet (UV) radiation, temperature extremes, toxins, and bacteria. Other important functions include sensory perception, immunologic surveillance, thermoregulation, and control of insensible fluid loss.
The skin consists of 2 mutually dependent layers, the epidermis and dermis, which rest on a fatty subcutaneous layer:
- Epidermis: This tough layer of cells is the outermost layer of skin. It gets its toughness from a protein called keratin. The epidermis has five layers:
- Stratum corneum is made up of dead, mature skin cells called keratinocytes. These cells are constantly shed and replaced by cells from the lower layers of the epidermis. These cells have lost most of their internal structures and organelles.
- Stratum lucidum is found in thicker skin and helps reduce friction between the stratum corneum and the stratum granulosum. It’s composed of dead, flattened cells.The skin is thicker in some areas (like the soles of your feet) and thinner in others; women also tend to have thinner skin than men do.
- Stratum granulosum is where keratin is formed. The cells in this layer also produce materials that prevent evaporation, which helps waterproof the skin.
- Stratum spinosum contains the keratin-producing cells that were formed in the stratum basale. Keratin is a major structural component of the outer layers of skin.
- Stratum basale forms the deepest layer. The cells of this layer continuously divide and form new keratinocytes to replace the ones that are constantly shed. This layer also contains melanocytes, which are the cells that produce skin coloring.
- Dermis: This lower layer of the skin contains collagen and elastic fibers that give strength to the skin. This layer is also where the vasculature and nerves live.
Together the epidermis and dermis form the cutaneous layer. The subcutaneous layer (area below the skin) lies underneath the cutaneous layer and is sometimes called the hypodermis or superficial fascia. It holds most of the body’s fat, so it varies in thickness from one person to another.Creases form over joints because the skin always folds the same way as the joints bend. The skin is thinner in those areas and is firmly attached to the underlying structures by connective tissue.
The skin also includes the structures that grow out of the skin, plus a couple of glands:
- Hair: The protein keratin forms hair. Hair has an inner layer (the cortex), which contains pigments that give it color, and an outer layer (the cuticle). It grows out of follicles, which are little pockets of epidermis in the dermis. The shape of the follicle determines whether hair is curly or straight. Each follicle contains a hair bulb from which the hair develops.
- Arrectorpili muscles connect the hair follicle to the skin.
- Nails: Keratin shows up again in the form of plates found on ends of the fingers and toes. Underneath each nail is a nail bed with a root at the proximal end (closer to the rest of the body).
- Sebaceous glands: These glands are connected to the hair follicles. They produce sebum, which is an oily substance that helps keeps the hair flexible.
- Sweat glands: Sweat glands are coiled tubular glands found in most of the skin. The secretory portion (the part that secretes the sweat) of each gland lies in the fascia with a duct that runs up to the surface of the skin.
Life expectancy in the most industrialized countries continues to increase and is expected to reach 100 years by about 2025. Women have longer average life expectancies than do men and can thus soon expect to spend more than one-third of their lifetimes in menopause. The skin is incredibly durable, but like all other systems, it eventually succumbs to the inexorable effects of aging. The skin is also the most visible indicator of age.
Your skin changes as you age. You might notice wrinkles, age spots and dryness. Your skin also becomes thinner and loses fat, making it less plump and smooth. It might take longer to heal, too.
The desire of many to look young for their age has led to the establishment of a large cosmetics industry. However, the features of appearance that primarily determine how old men or women look for their age and whether genetic or environmental factors predominately influence such features are now being understood as we do not have all the answers at present.
Many things cause our skin to age. Some things we cannot do anything about; others we can influence.
Skin ages in both men and women through parallel internal and external processes, which contribute simultaneously to a progressive loss of skin integrity.
How does our skin age?
Skin aging is a complex biological process influenced by combination of endogenous or intrinsic (genetics, cellular metabolism, hormone and metabolic processes) and exogenous or extrinsic (chronic light exposure, pollution, ionizing radiation, chemicals, toxins) factors.These factors lead together to cumulative structural and physiological alterations and progressive changes in each skin layer as well as changes in skin appearance, especially, on the sun-exposed skin areas
Skin that has aged due to intrinsic factors (mostly sun protected skin) will be thin and atrophic, finely wrinkled and dry while that due to sun damage shows a thickened epidermis, mottled discoloration, deep wrinkles, laxity, dullness and roughness.Although the fundamental mechanisms are still poorly understood, a growing body of evidence points toward the involvement of multiple pathways in the generation of aged skin.
The primary structural components of the dermis are collagen, elastin and glycosaminoglycans have been the subjects of the majority of anti-aging research and efforts for aesthetic-anti-aging treatments pertaining to the skin, from”anti-wrinkle creams” to various filling agents.
Skin changes that come with age,
These changes reflect not only the alterations in the skin per se but also fluctuations in tissues beneath the skin. Together they convey the effects of aging.
Skin changes that occur naturally as we age:
- Rough or coarser skin.
- Loss of elastin causes the skin to sag or become slack.
- Skin becomes more transparent. This is caused by thinning of the epidermis (surface layer of the skin).
- Skin becomes more fragile. This is caused by a flattening of the area where the epidermis and dermis (layer of skin under the epidermis) come together.
- Skin becomes more easily bruised. This is due to thinner blood vessel walls.
- Skin develops lesions such as benign tumors (seen in mostly fairer/Caucasian skin)
Changes below the skin also become evident as we age. They include:
- Loss of fat below the skin in the cheeks, temples, chin, nose, and eye area may result in loosening skin, sunken eyes, and a "skeletal" appearance.
- Bone loss, mostly around the mouth and chin, may become evident after age 60 and cause puckering of the skin around the mouth.
- Cartilage loss in the nose causes drooping of the nasal tip and accentuation of the bony structures in the nose.
From a treatment perspective the correction of the skin changes can be achieved to a large extent in a non-surgical manner but when correction of the changes in the subcutaneous region have to be made then it is usually done by surgical methods.
Your skin protects your body, but that's not all. It's the face you present to the world. When healthy, it's a source of beauty. Our skin is at the mercy of many forces as we age: sun, harsh weather, and bad habits.
One thing that we cannot change is the natural aging process. It plays a key role. With time, we all get visible lines on our face. It is natural for our face to lose some of its youthful fullness. We notice our skin becoming thinner and drier. Our genes largely control when these changes occur. The medical term for this type of aging is “intrinsic aging.”
However the “extrinsic aging” can be controlled to a large extent by the choices you make every day -- your lifestyle, diet, heredity, and other personal habits.
How your skin ages will depend on a variety of factors:
Apart from your genes your lifestyle, diet, amount of sleep, alcohol consumption etc will determine the speed with which you will age.
- Smoking - smoking can produce free radicals, once-healthy oxygen molecules that are now overactive and unstable. Free radicals damage cells, leading to, among other things, premature wrinkles. Simply put, smoking is bad for your skin: It's second only to the sun in causing premature wrinkles and dry skin. In fact, under a microscope you can see wrinkles in smokers as young as 20. Smoking reduces blood flow to the skin and contributes to the breakdown of collagen. Less collagen means more wrinkling. And yes, pursing your lips repeatedly encourages wrinkles, too. You can't reverse the damage, but you can stop it by quitting smoking.
- Diet - Watch your diet.Findings from a few studies suggest that eating foods rich in antioxidants, such as fish, fruits, and vegetables, seem to help protect skin and may help prevent damage that leads to premature skin aging. Findings from research studies also suggest that a diet containing lots of sugar or other refined carbohydrates can accelerate aging. Higher intakes of vitamin C and a lower intake of fats and carbohydrates are associated with better appearance as your skin ages. Changing your diet will help your looks. Some studies suggest that to avoid breakouts, go for complex carbohydrates (like whole grains and pasta) and healthy protein. Dairy products are also known to cause acne flares.
- Alcohol – Too much alcohol could be bad for your skin. Alcohol tends to dehydrate the skin, and in time, damages the skin. This can make us look older.
- Sleep debt - There are many, many, short-term and long-term consequences of sleep deprivation. The most clinically apparent ones – swollen, sunken eyes; dark circles; and pale, dehydrated skin – are obvious. Several studies of prolonged sleep deprivation suggest a break in skin barrier function and mucous membranes. In fact, the reduction of sleep time affects the composition and integrity of various systems. Rats subjected to prolonged periods of sleep loss in a study developed ulcerative lesions on their paws and tails, and susceptibility to bacterial infection.Sleep deprivation can be caused by artificial light, shift work, sleep disturbances, and social life. To maintain a healthy skin it is important to keep in mind “Beauty sleep is both necessary and irreplaceable”.
- Exercise – Many studies have shown the beneficial effects of regular exercise on skin. Moderate exercise can improve circulation and boost the immune system. This, in turn, may give the skin a more-youthful appearance.
- Sun protection - Exposure to sunlight is the single biggest culprit in aging skin.Over time, the sun's ultraviolet (UV) light damages certain fibers in the skin called elastin. The breakdown of elastin fibers causes the skin to sag, stretch, and lose its ability to snap back after stretching. The skin also bruises and tears more easily and takes longer to heal. So while sun damage may not show when you're young, it will later in life.Nothing can completely undo sun damage, although the skin can sometimes repair itself. So, it's never too late to begin protecting yourself from sun exposure and skin cancer. You can delay changes associated with aging by staying out of the sun, covering up, wearing a hat, and making a habit of using sunscreen.
- Moisturize your skin - Dry skin can cause all sorts of discomfort, including peeling, flaking, cracking, redness and itching. The obvious way to get rid of dry skin externally is to moisturize regularly. The best way to moisturize is to apply the moisturizer immediately after your bath when the skin is slightly damp.A moisturizer traps water in our skin, giving it a more youthful appearance.It helps to smoothe the skin surface by flattening the “valleys” between the skin contour ridges. It also makes the skin surface soft, more extensible, and pliable. The moisturizing action of emollients is evident maximum 30 min–1 h after their use and usually lasts for 4 h. Other ways to improve the skin moisturizing is to choose foods you eat based on how they will help your skin.
- Use mild facial cleansers - Gentle cleansing helps skin look its best. To gently cleanse your face, wet it with lukewarm water. Then apply a mild cleanser, gently applying the cleanser in a circular motion with your fingertips. Finish by completely rinsing off the cleanser and gently patting your face dry with a clean towel
- Avoid scrubbing your face - Scrubbing irritates your skin, which can worsen any skin condition, including acne. So it is best to avoid scrubs for the face.
- Control stress - Finding healthy ways to manage stress can help your skin, too. Some skin diseases like psoriasis and atopic dermatitis (eczema) often appear for the first time when someone feels really stressed. Stress can also cause flare-ups of many skin conditions, including acne, eczema, psoriasis, and rosacea.