Written By: Zenani Sizane
Today, we'll look at the three main skin layers. It's important to understand how the three different types of skin layers work, because it will give you a better understanding of why things like stretch marks, wound healing, and even cellulite form on the skin, and you'll be able to use the right products for those specific problem areas.
LAYERS OF THE SKIN
The skin is a specialized and complex set of tissues divided into three layers: the epidermis, dermis and hypodermis, also known as the subcutaneous layer. There are several different types of cells in the skin, the most important of which are keratinocytes, melanocytes, fibroblasts and a variety of immune cells (Langerhans, migrating mononuclear cells and mast cells.
In addition to these various cell types, the skin also contains connective tissues that are rich in extra cellular matrix, the components of which are responsible for the flexibility-its suppleness and elasticity. Other important functions such as hydration, temperature regulation and the regulation of the skin permeability depend on specific cells and the chemical composition of the ECM.
These regulators functions linked to the interaction between the cells and the chemicals in the skin through special receptors located on the membrane of each cell. These receptors are like antennae that helps cells communicate with each other and with their environment.
They are also able to bind with various chemical components that pass between cells. Among these chemical substances are certain ingredients used in cosmetics such as retinol, they interact with the cells and perform a variety of therapeutic functions through receptors that do not function. The skin’s physiological performance is impaired, accelerating damage and deterioration such as aging.
While work with receptors is a concept studied more in medicine and pharmaceuticals, in cosmetics the role of receptors for retinol effectiveness e.g. is well established.
As much mentioned before the skin is divided in three different layers, the Epidermis, the dermis and the Hypodermis and each of those layers are also divided in good number of different layers. In the following section of the blog, we are going to unpack and take look at each layer and its individual function.
THE EPIDERMIS
Understanding the epidermis is important for discussing product penetration. The epidermis gives the skin its glow, youthfulness, texture, and good looks. The epidermis is the part of the skin visible to the naked eye. It is a very thin layer which is approximately 25 to 30 cell layers deep. Its thickness varies from 0.063 inch (1.6mm) on the soles of the feet to 0.002 inches (0.04mm) on the eyelids.
The epidermis contains a variety of cells, including keratinocytes, which engages in a constant process of reproduction to replace exfoliated cells, Langerhans cells for immunological protection, melanocytes for skin color, and Merkel cells that involves in the function of touch.
The epidermis is the layer of the skin to which products are applied to and the one with which an individual and (cosmetics) comes most in contact when cleansing, exfoliating, healing and hydrating. It is responsible for the skin’s health, protecting it from moisture loss and the penetration of bacteria. UV rays, acne conditions, visible skin disease, cigarette, smoke, pollution and skin cancer all affect this layer.
is an active tissue that synthesizes lipids and contains all the individual components required to form the protective barrier layer. Since the epidermis represents the outermost layer of the skin, it acts as the initial barrier to oxidant assault.
The epidermis has a higher protective and antioxidant capacity than the dermis because it houses essential free radical scavengers such as Vitamin E and C and superoxide dismutase. This layer also contains large amounts of glycosaminoglycans and ceramides. The epidermis is divided into five sublayers of cells, all of which play an active role in maintaining healthy skin.
Epidermal cells formed in the germinative layer and move upward toward the stratum corneum layer, in their upward migration, the epidermal cells undergo a number of chemical modifications, transforming from soft protoplasmic cells into flat surface (scales) made of keratin that rub off.
The epidermis holds a large amount of water. The layer with the highest water content is the germinative layer holding 80 percent. Each layer has less water as a percentage of its total chemical composition with the stratum corneum layer containing only 10 percent to 15 percent water. Water is held in the cells cytoplasmic gel and in the intercellular channels (spaces between the cells).
The younger the body the more water there is in the skin. The skin’s capacity to retain water decreases with age, making the skin more vulnerable to dehydration and wrinkles. In a younger person, it takes approximately 28 days for a cell to travel from the germinative to the corneum layer. With age, the speed of this process drops.
It is estimated that after the age of 50 it takes about 37 days to complete the same process. In terms of skin aging this indicates that stimulating skin function, either through facial massages or through cosmetic product activity would improve cellular metabolism. The 28-and 37-day time span is also important when it comes to skin sensitivity and the misuse of facial scrubs.
It takes 28 days or more for a cell to reach the surface of the skin, then we are exfoliating one layer of dead cells a day. Depending on the harshness of the material, the use of scrubs may remove more layers of surface dead cells than appropriate, increasing skin and sensitivity. Furthermore, the misuse of scrubs may exuberate oil gland activity thereby increasing oil production the opposite of what one generally wishes to achieve.
Understanding the epidermal layers allows us to understand some of the problems of dehydration, sensitivity, aging and pigmentation, which in turn helps associate product and ingredient effectiveness with skin requirements.
The Epidermal Layers
Keratinocytes are the predominant cell species found in the epidermis and are found in the four epidermal layers from germinative to stratum lucidum. The epidermis' primary function is to produce the uppermost layer, the stratum corneum layer. A faulty keratinocyte formation system cannot produce an aesthetically pleasing stratum corneum layer. As a result, it appears that the proper metabolism of keratinocytes in order to generate a healthy stratum corneum layer is a key factor for beautiful skin.
This is necessary to prevent moisture loss and the penetration of microbes and chemical irritants. This layer is thought to be so important for product penetration, skin hydration, and skin sensitivity reduction that it is frequently studied separately from the other epidermal layers. What we see as our skin is the stratum corneum layer. It is made up of 18 to 23 layers of flattened dead cells (also known as corneocytes) that are firmly cemented together in healthy, young skin.
.png)
The number of layers is determined by a number of factors, including oil secretion and exfoliation rate. The stratum corneum is thickest on the palms and soles of the feet and thinnest on the eyelids. The stratum corneum is divided into two distinct layers: the compact layer, in which the breakdown of cellular union causes exfoliation, allowing for the continuous elimination of cells; and the loose layer, in which the breakdown of cellular union causes exfoliation, allowing for the continuous elimination of cells. As the corneocytes gradually detach, numerous spaces between the cells form, allowing bacteria on the skin to thrive and feed on the remaining corneocytes and lipids.
These bacteria have adapted to the acidic stratum corneum environment. Other bacteria, known as transients, may exist on the skin's surface, but the pH conditions are unfavorable for their growth and proliferation. The natural process of cellular exfoliation is enzymatically controlled. Specific enzymes break down the bonds that hold the corneocytes together, allowing them to slough off. If this process fails, too many dead cells accumulate on the skin's surface, causing hyperkeratosis (too much keratin) and leaving the skin looking thick, rough, and unappealing.
The stratum corneum layer only returns about 10 to 15% of its original moisture.
Its main functions are to keep the skin hydrated by preventing water from evaporating through the skin (trans epidermal water loss) and to keep foreign matter from penetrating the skin.
Lipids and ceramides, as well as glycol-proteins, desmosomes, peptide breakdown products, sebaceous products, and active enzymes, hold the cells together and surround them.
By acting as a barrier, trapping water, and preventing excessive water loss, intercellular lipids play a critical role in the skin's water-retention properties.
Ceramides account for up to 40% of total intercellular lipids and play an important role in the skin's water retention capacity.
The stratum corneum layer contains a natural moisturizing factor (NMF) composed of hydro-soluble (able to dissolve in water) and hydroscopic (able to retain water) substances that regulate the selective permeability of the stratum corneum. The NMF is composed of approximately 40% free amino acids, approximately 12% PCA, 12% lactose, 7% urea, and approximately 30% of a wide range of other materials. Exposure to harsh detergents and climatic conditions can result in decreased NMF levels, leaving the skin fragile and dry.
The thickness of the stratum corneum layer, the proper arrangement of its surface cells, and the strength of the cellular cement all play a significant role in a product's or ingredient's ability to penetrate. A well-formed stratum corneum is thin and compact, with an orderly cellular structure that resembles a basket-weave and produces a strong barrier function.
The natural barrier function of the skin is reduced when the stratum corneum layer is thick and its cells are arranged in a compact, uneven pattern, allowing potential irritants to penetrate. This is one of the reasons why products can cause irritation or a burning sensation. Sensitivity may occur when the skin is excessively moist because the barrier has been disrupted, making it easier for certain irritants to penetrate. Alpha Hydroxy Acids (AHAs) and other ingredients restructure or normalize an abnormal stratum corneum, giving it a healthier structure and restoring its protective capabilities.
Melanocyte cells produce skin pigment, or melanin, in the epidermis's deepest layer. The pigment is then transferred to keratinocytes, which gives the skin its color. Skin or UV light exposure (e.g., sunbathing) and/or hormonal imbalances can cause excessive melanin production.
In the first case, melanocytes produce more melanin to protect the skin from free radical damage. When UV light exposure is stopped, cellular migration and normal exfoliation allow the skin to gradually eliminate the pigment cells and return to its normal color, e.g., the skin returns to its normal color a few months after summer vacation. In the second case, hormonal imbalances cause shifts that stimulate increased melanocyte activity, resulting in an excess of pigment.
This is most frequently seen during pregnancy (melasma). Furthermore, severe irritation reactions, like hormones, can stimulate excessive melanin production, resulting in post-inflammatory hyperpigmentation (PIH). Langerhans cells provide immunological protection in the epidermis. They detect foreign bodies that have penetrated the epidermis, capture them, and transport them to lymphocytes in the lymphatic system.
An immune response is then elicited, which neutralizes and eventually eliminates the foreign element. Merkel cells, which are located between the keratinocytes, detect touch. Merkel cells are epidermal cells that have been modified and are linked to a receptor.
The epidermal layer's complexity is astounding, especially given its thinness. In addition to the various cells present, their individual functions, and their relationship to one another, the skin is constantly active in the following ways: Cellular receptors are interacting, and a slew of physiological and chemical interactions are taking place.
All of these elements must be in proper balance in order to ensure proper keratinocyte metabolism and functioning. The beauty and health of the skin is jeopardized in the absence of such balance. As a result, caring for the skin and avoiding unnecessary harshness become critical for the health and beauty of the skin.
THE DERMIS
The dermis is the skin's second layer. Its thickness ranges from 10 to 40 times that of the epidermis. The dermis contains skin appendages, hair follicles, sebaceous glands, two types of sweat glands (eccrine and apocrine), and a complex capillary and nerve network.
The dermis is composed of 80% water, elastin fibers that provide elastic properties, and collagen fibers that provide a structural framework. Collagen accounts for roughly 70% of dermal proteins and provides resistance, resilience, and fraction.
There are approximately 20 different types of collagen fibers identified, with collagen I and III being the most common in the skin. When the repair process begins with the production of very thin collagen fibers, the wound heals optimally.
When wound healing begins with thicker forms of collagen, keloids form. In addition to collagen and elastin, the dermis contains a variety of other fibers known as structural glycoproteins and a group of chemicals known as glycosaminoglycans. These are in charge of hydration, flexibility, and water retention. They also regulate permeability, provide pressure resistance, and are in charge of protein orientation.
The dermis provides energy and nutrition to the viable epidermis through its vast network of capillaries and blood vessels, and it also plays an important role in healing and thermoregulation. It is in charge of the skin's supporting framework and elasticity. This, in turn, is dependent on a well-balanced water content in the dermis and other skin layers.
The dermis serves as a water storage site to aid in this vital hydration. It also protects the body from mechanical injury and serves as an important sensory receptor and internal regulator. Langerhans cells, which are responsible for immunoprotection, can also be found in the dermis.
The dermis is a thick connective membrane that is crisscrossed by blood vessels, lymphatic vessels, nerve fibers, and numerous sensory nerve endings. The dermis's two main components, collagen and elastin protein fibers, act as a structural support system for the nerve fibers, hair follicles, blood vessels, and oil and sweat glands located in this layer, giving the skin strength and elasticity.
Collagen is the primary component of the dermis and is composed of a chain of amino acids that includes alanine, arginine, lysine, glycine, proline, and hydroxy-proline. Its production begins with the production of pro collagen, which is then modified and transformed into regular collagen. Pro collagen is extremely hydroscopic, binding many times its weight in water.
A decrease in procollagen content over time may be linked to the increased dryness, wrinkles, and lack of elasticity seen in mature skin. Different types of elastin fibers account for 2 to 4% of the dermis in healthy or undamaged skin. Under a microscope, elastin appears as short, overlapping fibers that form an irregular network within the dermis, primarily concentrated in the layer's lowest segments, and provides skin elasticity and resilience.
The importance of elastin is disproportionate to its low concentration in the dermis. Various glycoproteins and glycosaminoglycans fill the space between collagen and elastin. These are an important component of the ECM and provide structural support to the dermis.
Glycoproteins are molecules made up of a protein and a carbohydrate. Fibronectin is the most common glycoprotein. This molecule is important for wound healing because it plays an important role in cell adhesion, growth, migration, and differentiation. Glycosaminoglycans are large carbohydrates that can bind to proteins to form proteoglycans (a type of glycoprotein) or can be found as standalone molecules in both the dermis and the epidermis.
Glycosaminoglycans are fundamental dermal materials that provide support, lubrication, and an optimal environment for dermal cell development. They also have a high water binding capacity, which is important for the skin's turgor, water content, and elasticity.
The most common glycosaminoglycan is hyaluronic acid: as we age, our skin's glycosaminoglycan content decreases, reducing our skin's ability to retain water and increasing our proclivity for dryness.
The dermal layer's proper functioning, as well as its water content, is responsible for the skin's color, smoothness, and elasticity. A healthy dermis is essential for a youthful appearance and beautiful skin.
THE HYPODERMIS
The hypodermis, also known as the subcutaneous fascia, is the skin's third and final layer. It connects the dermis to the deeper tissues known as fascia and muscle. This layer gives the skin its shape and functions as a thermal insulator, shock absorber, and nutritional depot, storing nutrients until they are needed. The layer is firmly attached to the dermis's lower surface but loosely bound to its underlying structure, allowing the skin to move over the deeper fascia.
Collagen fibers surround the fat lobules of the tissue, which support vascular networks, lymph vessels, and nerves from the underlining tissues to the dermis. It does not appear on the eyelids, nipples, genitals, or shins because the skin is too thin.
In general, the layer is not normally considered when developing cosmetic products, except when attempting to reduce cellulite and/or the overall thickness of various body parts, such as the thighs and belly in the case of slimming products.
Recent research has shown that nutrients taken orally, such as fat-soluble anti-oxidants, can be stored in this tissue and later transferred to the dermis and epidermis to minimize free radical damage.
Finally, it should be noted that working with this layer of skin can be beneficial in other therapeutic areas such as Rolfing.(Rolfing is a type of alternative medicine that benefits the human body's energy field when it is aligned with the earth's gravitational field.) in other therapeutic areas like Rolfing.( Rolfing is a form of alternative medicine, how the human body’s energy field can benefit from when aligned with the earth’s gravitational field)
Skin must be healthy and well-cared for in order to be beautiful.
The End.
Commentaires