Skin Anatomy and Function
In its entirety, the skin
is comprised of three distinctive layers, the epidermis, the dermis
and hypodermis. Each layer exhibits unique cellular makeup and
physiological function.
The epidermis (outer-most
layer) is comprised of keratin, which strengthens the skin, and melanin,
found in the basal layer of the epidermis, responsible for depth of skin color.
Important cellular components in immune recognition of pathogens, called
Langerhans cells, also reside in the epidermis. The epidermis provides protection
against the environment; the stratum corneum being the primary barrier.
The dermis is directly
below the epidermis and provides a kind of scaffold for strength and support.
Unlike the epidermis, the dermis contains nerves, blood vessels and fibroblasts
that provide sensory receptors, deliver nutrients, and maintain the structural
foundation of the skin. The most abundant connective material within the dermis
is collagen, a fiberous protein whose primary function is to maintain
skin firmness. Elastin protein fibers combine with collagen to give the
skin elasticity. The base of the dermis is composed of substances such as
complex sugars (glycosaminoglycans), glycoproteins, hyaluronic
acid, and chondroitin sulphate. These substances combined form a
"cementing and gelling" base that binds to water molecules, allows
nutrients and oxygen into the tissue and protects the dermal structural layer.
It is within the dermis that new cells are produced and eventually migrate
toward the outer layers (the epidermis).
The bottom layer of the
skin is the hypodermis. It contains adipocytes (fat cells) that insulate the
body and help to preserve heat, as well as other connective tissues.
Skin contains the sebaceous
glands and sweat glands (eccrine and apocrine), which help to
prevent dryness, protect skin against bacteria, and maintain core body
temperature (thermoregulation).
Intrinsic and Extrinsic Factors of Skin
Aging
Skin aging has many
reasons. The researchers differentiate between two kinds of factors. First,
intrinsic factors, which can hardly or not at all, can be affected by the
people, like biological aging. Characteristics are, e.g. a slowed cell
division and energy metabolism. Further intrinsic factors are related to genetic
predispositions. For example, skin ages differently whether it is female or
male skin. Hormonal alterations during the puberty or the menopause can also
affect skin aging.
Second, there are extrinsic
factors, like diet, environment, psychological factors, and more. UVA-rays are,
for example, one of the main reasons for skin aging process. They penetrate
deep into the skin layers, destroy the elastic fibers in the connective tissue
and thus cause the skin to sag. Stress and the personal lifestyle, e.g.
smoking, can have negative effects as well.
Among other extrinsic
factors there are the follows: excess alcohol consumption, tobacco abuse, and environmental
pollution. In addition, few people realize that as their body weight increases
and their blood sugar levels rise, biochemical reactions disrupt the
very structural framework of their skin. Combined, these factors lead to
cumulative deterioration in skin appearance and function.
Within the skin, aging is
associated with a loss of fibrous tissue, slower rate of cellular renewal, and
a reduced vascular and glandular network. Barrier function that maintains
cellular hydration also becomes impaired. The subcutaneous tissue (hypodermis)
flattens, particularly in the face, hands and feet.
Depending upon ones
genetic makeup and lifestyle, normal physiological functions within the skin
may decline by more than 50% by middle age.
Men vs. Women
Men and women are both human beings, and it seems
that the skin characteristics should not be unlike. However, the processes of
aging differ in male and female skin.
In men, there is a gradual thinning of the skin with
increasing age of approximately 1% per year. The thickness of most women's
skins remains surprisingly constant until the menopause, after which there is a
significant and sometimes dramatic thinning with aging.
There is a relationship between skin thickness and
collagen content in men of all ages. A similar relationship exists among women
over 60 years of age, but it is much less evident in younger women.
In adult skin, the features of aging are closely
related to the total collagen content, which in both sexes decreases with aging,
but at different rates. In later life, woman’s skin may look older than man’s
of the same age and with similar experience to the sun exposure, partly because
their skin has lower collagen content to start with. Another reason for the
gender difference in skin collagen content is related to the difference in male
hormone production between men and women. In women, estrogen and androgen
output from the ovaries and adrenal glands is reduced after menopause,
resulting in decreased collagen synthesis and repair.
Skin Aging Timeline
- < 15
- Nearly perfect skin. Smooth texture, pores small. Excellent repair
capabilities. Low sebaceous gland activity. Skin hydration good.
- 15-25
- Acne key factor in surface texture. Fine lines start to appear, pore
size increasing. High sebaceous gland activity. Mild drop in dermal
repair, immune system and collagen synthesis. Strong cohesion between skin
layers and rapid cell turnover. Small drop in skin hydration, noticed
particularly in winter.
- 25-45
- More fine lines and appearance of first wrinkles (photodamage). Early signs
of sagging near the eye. Some loss of elasticity. Adult acne. Moderate
decrease in dermal repair, resulting in less collagen and increasing
accumulation of damaged corrective tissue. Noticeable and significant drop
in skin hydration.
- 45-55
- More wrinkles, rough texture. Sallow yellow color begins to appear. Pores
and age spots enlarge and define. Sagging near eye and cheek. Significant
decrease in dermal repair and immune system. Continued dermal degradation.
Cohesion between skin layers continues to decline. Thinning of epidermis
and stratum corneum. Skin tends now to be dry.
- 55-70
- Wrinkles and fine lines in abundance. Uneven color, pigmentation. Sagging
worsens. Dark circles under eye. Compromised dermal repair, abundance of
damaged connective tissue. Low production of collagen and sebum. Increased
local over-production of melanin.
- 70+ - Extremely dry skin, extended and visible blood vessels, age spots in the face, on the neck and on the back of the hands
Diet for Healthy Skin
As
skin is the "visual" organ, the beauty industry's primary objective
is to improve the appearance of skin with sophisticated topical treatments and
interventions. However, often overlooked is the need support the health and
beauty of skin from within through proper nutrition.
In
addition to the well-documented role of a wholesome, plant-based diet in
maintaining the youthful vivacity of the skin, modern nutritional science is
elucidating the relationship between specific nutrients and optimal skin
health.
Sadly,
the typical North American diet falls considerably short of providing the
nutritional composition needed to keep skin healthy and vibrant.
- Macronutrient
Composition and Glycemic Load - The North American diet contains excessive
amounts of simple carbohydrates and saturated fats. Not surprisingly, this
dietary pattern correlates with an increased appearance of skin wrinkles. The
glycemic index measures how rapidly and significantly foods cause
blood sugar elevations following consumption. Epidemiology data suggest
that a high glycemic diet may contribute to inflammatory skin conditions
such as acne, rosacea, psoriasis, and eczema as well.
Insulin resistance and inflammation disrupt sebum production, cause collagen malformation, and excite the epidermal growth factor receptor, which is involved in tissue renewal, but can also stimulate inflammatory reactions in the skin cells. When sugar comes in contact with collagen (a protein), a devastating reaction, called glycation, occurs resulting in the formation of tissue-destroying advanced glycation end products (AGES). Glycation occurs in all tissues of the body, but is accelerated by a high sugar diet and, within the skin, excessive sun exposure.
Protein glycation and AGE formation are accompanied by increased free radical activity in skin collagen, which accelerates skin aging. All of these changes create an environment within the skin that favors degradation of collagen, compromising the integrity and regeneration of skin tissue.
- Fatty acid composition – Within the skin, fatty acids make up an integral component of cell walls (membranes) that help maintain cell structure and function. Clinical studies show that the healthy balance of fatty acids in skin dramatically decreases with aging and increased oxidative stress, such as that caused by chronic sun exposure. Therefore obtaining the right amount (and type) of fats through diet or supplementation is critical to maintain healthy skin as we age. Traditional and non-Westernized diets offer a more balanced intake of omega-6 to omega-3 fatty acids (typically at a ratio of about 4:1). Today, the North American diet provides a ratio of about 15:1 or more of omega-6's to omega-3's. Excessive amounts of the omega-6 fat arachidonic acid, found in relatively high quantities in egg yolks, poultry skin, and organ meats from animals fed corn-based diets have a pro-inflammatory effect in the body (including the skin). Conversely, fish oil rich in the omega-3 oils eicosapentaenoic and docosahexaenoic acids (EPA and DHA) inhibit the production of inflammatory metabolites. Due to their ability to modulate inflammation, long-chain omega-3 fatty acids are effective in the management of inflammatory skin conditions, such as acne, psoriasis, eczema, and rosacea.
- Micronutrient & Antioxidant density - For some time, nutrition experts have recommended choosing whole foods that are micronutrient- and antioxidant-dense over commercially-manufactured, overly processed foods negligible in micronutrients yet rich in fat and carbohydrate calories. This is a critical consideration for skin health as well. Clinical studies have shown that catechins from green tea, anthocyanins from dark berries and red cabbage, bioflavonoids from citrus, carotenoids such as lycopene and lutein from tomatoes, reservratrol from red wine and genistein from soy offer potent secondary antioxidant protection in the skin. By including these types of foods more often in the diet, the antioxidant defenses in the skin can be optimized.
- Sodium and Hypertension – The North American diet relies heavily on over-processed, salty foods and some studies suggest that high sodium intake increases the risk of developing hypertension. Studies have shown that those with borderline and established hypertension have significantly lower skin capillary densities than non-hypertensive subjects. A recent trial proved that by reducing sodium intake in hypertensive subjects, even modestly, microcirculation and capillary densities in the skin can be improved.
- Caloric Intake – Data indicate that calorie restriction (CR) promotes longevity through improving body composition and optimizing metabolic function. Caloric restriction may promote healthier skin aging due to improved skin cell renewal and repair mechanisms as well. Those interested in reading about the numerous benefits associated with caloric restriction should review Life Extension's Caloric Restriction protocol.
Other Recommendations
- Protect yourself from the sun. In our world of ozone holes and 30+ sunscreens, many people have come to think of the sun as an enemy to the skin. Yet the sun, besides being the source of energy for mind and body, also nourishes the skin. It’s the best source of Vitamin D, which is necessary for calcium absorption and healthy bones. Doctors today recommend 15 minutes of direct exposure to the sun on the hands and face to absorb the minimum daily requirement of Vitamin D. Over-protecting from sun is not a good idea. The challenge is to maximize the benefit from sun and at the same time protect it from damage.
While people with Caucasian skin definitely should
avoid direct exposure to the midday sun, short periods of exposure to the early
morning sun is soothing and mild on the skin, and allows even very sensitive
skin to absorb necessary Vitamin D. It is recommended avoiding long exposure to
the sun whenever you are angry, hungry or emotionally upset, as these factors
increase heat in the body and make the skin more sensitive to sun damage. At
these times it's important to protect yourself by wearing a hat and sunglasses.
It's also a good idea to cool the body from the inside if your skin is very
photosensitive. Eating green leafy vegetables and fruits such as raisins,
pears, apples, and pomegranates, for instance, will help nourish and restore
balance to the skin.
- Avoid Chemicals. Harsh chemicals in your shampoo, skin products,
or soaps irritate the skin. A strong preservative or antibacterial agent
in skin-care products, for instance, kills harmful bacteria but at the
same time destroys enzymes that trigger absorption and lubrication. The
result might be permanent dry patches, oversensitive skin, or
susceptibility to sun damage. Even synthetic aromas in skin products can
be irritating because they affect your emotions.
- Soothe Away Stress. Chronic stress and negative emotions affect our skin, damaging the moisture balance and accelerating its premature thinning. If the stress is not brought into balance, the skin also starts to shrink, resulting in wrinkles and stress lines. You want to see the direct link between emotions and skin? Just notice how anger or embarrassment can make your face turn red.
Physical stress can be caused by exercising or working
too much, or straining the body over a significant period of time. Like mental
stress, this causes the drying out of skin moisture resulting in rough, aged
skin.
- Rehydrate from the inside and outside. It’s important to moisturize your skin from the inside to provide necessary nutrients and to keep the inner layers of the skin from drying out. Drink lots of water, but add some spices to the water to help the water get absorbed and transported to the skin. In cold weather, it is recommended drinking hot water, as it opens the channels and helps clear away toxins.
For external rebalancing you can use natural oils like
olive oil or avocado oil, which
will bolster the natural lipid defense found between your cells. This makes the
skin more pliable and prevents water from escaping from the layers of skin. Humectants such as glycerin, lactic
acid, and sugars soak up water from the environment and carry it where needed.
They will leave your skin soft and smooth.
Moisturize your skin
immediately after cleansing or rinsing your face. Oily skin doesn’t necessarily mean hydrated skin.
When you give your face a nice drink of water, it becomes the best time to add
the moisturizer to lock in the water instead of block it out.
Use a pH adjust cleanser. Many liquid soaps are
alkaline and have a high pH. Your skin does not like alkaline ingredients and
will lose its integrity if used on a regular basis. Acidic cleansers are best
for your skin layers. Most liquid cleansers are pH adjusted below 6 while bar
soaps typically have a high pH.
Sources and Additional
Information:
