Welcome to my very first post on my blog “Chloe in The Cosmetics +84”! As a self-confessed beauty junkie, I’m excited to take you on my journey through the dynamic and challenging world of cosmetics. Whether you’re a fellow beauty enthusiast or just curious about what makes the products we put on our skin so fascinating, I’m thrilled to have you here!
In this first post, we’re going back to the basics and talking about the skin - our body’s largest organ and the first line of defense against the world around us. It's a fascinating topic that’s often overlooked, but understanding the structure and function of the skin is the key to unlocking healthy, glowing, and beautiful skin. We’ll explore everything from the layers of the skin to its essential functions.
So grab a cup of tea, sit back, and let’s delve into the wonderful world of skin anatomy together!
SKIN STRUCTURE
Human skin consists of three layers, namely the epidermis, dermis, and hypodermis, described from the outermost to the innermost layers, in Figure A1.1.
Figure A1.1. Three layers of human skin
Epidermis:
The epidermis is the outermost layer of the skin, serving as the first line of defense against external factors and loss of internal fluids. It is nourished by the diffusion of intercellular fluids from the dermal vasculature. The epidermis is composed mostly of keratinocytes (about 90-95%), which undergo distinct stages of differentiation and distribute in five sub-layers from the bottom to the upper portions of the epidermis: the stratum basale, stratum spinosum, stratum granulosum, stratum lucidum, and stratum corneum.
Figure A1.2. Layers of the epidermal human skin
Stratum basale: Keratinocytes in this layer are produced constantly by stem cells known as clonogenic cells, making it the site of active keratinocyte production. Melanocytes (about 5% of the epidermis), which synthesize melanin from tyrosine - an amino acid and store it in melanosomes, are also present in this layer. Melanin is transferred from melanosomes into keratinocytes via the dendritic process, protecting the skin from damage caused by UV radiation. Merkel cells, which are epithelial neuroendocrine cells, serve as slow-adapting mechanoreceptors.
Stratum spinosum: In this layer, keratinocytes are differentiated from those of the basal layer and adhere to each other through desmosomes, which help maintain the structural integrity of the skin. The layer also contains Langerhans cells, antigen-presenting dendritic cells that capture antigens and present them to T lymphocytes to activate the immune system against pathogens.
Stratum granulosum: This layer contains water-insoluble keratohyalin granules, which provide an impermeable layer that protects the body from external particles. Glycolipids found in the lamellar granules are released to the surface of the cells, acting as a glue to hold the cells together. These two proteins give the stratum granulosum its granular look and make up most of the keratinocyte mass in the layer.
Stratum lucidum: This layer contains flattened or dead keratinocytes that are then transferred into the stratum corneum. Eleidin, a clear protein rich in lipids generated from keratohyalin, is tightly packed within these cells, giving them their translucent appearance and serving as a water barrier.
Stratum corneum: The outermost layer of the skin, which is also the most visible, is composed of flattened, dead cells known as corneocytes that have shed their nuclei in a process called desquamation. Defensins, which are secreted by neutrophils, act as an innate immunity of skin by providing a phagocyte-mediated host defense against penetration of viruses, fungi, and bacteria pathogenic microorganisms. Cosmetic procedures like microdermabrasion aim to remove some of the dry, top layers of the skin, keeping it looking "fresh" and healthy.
The turnover of basal cells from keratinocyte production to the desquamation process or loss of corneocytes takes 28 days, with the first 14 days for migration from the basal layer to the cornified layer and the last 14 days for terminal differentiation in the stratum corneum. Therefore, it is important to exfoliate the skin, helping the elimination of the corneocytes.
A separation between the epidermis and dermis is a basement layer or dermo-epidermal junction (DEJ), serving as epidermal-dermal adherence, mechanical support for the epidermis and a barrier to the exchange of cells and of some large molecules across the junction.
Dermis:
The dermis layer is one of the most important layers of the human skin. It is composed of main collagen, elastin fibers, blood vessels, nerves, and specialized cells that provide oxygen, nutrition supplies, and cutaneous sensation for the epidermis.
If you're concerned about maintaining your skin's elasticity and firmness, then the dermis layer is an important target for anti-aging treatments. As we age, the collagen and elastin fibers in the dermis layer become less dense and less organized, resulting in the loss of elasticity and the formation of wrinkles and fine lines.
The dermis is composed of two main layers, the thinner superficial papillary layers, and the deeper and thicker reticular layer.
Figure A1.3. Two main layers of the dermis
Papillary layer:
Connective tissues in this layer arrange loosely and areolar, in which collagen and elastin fibers connect with a lot of ground substances supporting the skin’s hydration. Fibroblasts, a modest number of fat cells (adipocytes), and an abundance of tiny blood capillaries are present in the papillary layer. Phagocytes, which are defense cells, are also present in the papillary layer and aid in the battle against bacteria that have penetrated the skin.
Reticular layer:
It is a dense and irregular network composed mainly of dense irregular connective tissue, collagen, and elastin fibers, which provide strength, support, and elasticity to the skin.
Elastin and collagen fibers are important components of the extracellular matrix of the skin's dermis layer.
Collagen fibers provide structural support and strength to the skin, while elastin fibers allow the skin to stretch and then return to its original shape. Collagen is the most abundant protein in the skin and is responsible for maintaining its firmness and elasticity.
Elastin provides the skin with the ability to stretch and recoil, and it plays a key role in maintaining the skin's shape and texture. Together, collagen and elastin fibers are crucial in maintaining the skin's overall health and appearance.
But there's more to the dermis layer than just collagen and elastin. The extracellular matrix of the dermis layer also contains glycosaminoglycans, proteoglycans, and hyaluronic acid, which play essential roles in skin hydration, elasticity, and overall health.
Lastly, the reticular layer of the dermis contains a variety of blood vessels, lymphatics, nerves, hair follicles, and sweat glands that regulate body temperature and play a crucial role in sensory perception.
Hypodermis
The hypodermis, also known as the subcutaneous tissues, is made up of well-vascularized, loose, areolar connective tissue and adipose tissues serving as a means of fat storage and providing insulation and cushioning for the integument. Additionally, it regulates body temperature by storing and releasing heat. Although it is often overlooked, the hypodermis plays a critical role in keeping us comfortable and protected.
SKIN FUNCTIONS
The skin is a remarkable organ that serves a range of purposes, from shielding us against harmful pollutants and UV radiation to maintaining our body temperature through thermoregulation.
Protection: The skin provides a barrier, safeguarding us against potentially damaging external factors such as microorganisms and UV radiation that could harm our tissues and cells.
Thermoregulation: The skin regulates our body temperature by means of a process called thermoregulation, which involves the dilation or constriction of blood vessels and the production of sweat to keep our internal temperature at a comfortable level, even in the face of extreme weather conditions.
Sensory: The skin enables us to perceive touch, temperature, and pain, allowing us to experience the warmth of a loved one's embrace or to know when to withdraw our hand from a hot surface.
Vitamin D synthesis: When exposed to sunlight, the skin produces vitamin D, which is crucial for maintaining healthy bones and other vital bodily functions.
It is worth acknowledging and appreciating the various ways in which our skin serves us every day. And to ensure that it stays healthy and functional, we must offer it the care and attention that it deserves.
SKINCARE
The world of skincare is spectacular and unlimited to talk about, but here I’ll just mention three important steps in the skincare routine.
Cleansing:
Cleansing is an essential step in any skincare routine as it helps to deep clean the skin and remove excess dirt, makeup, and impurities that accumulate throughout the day. Failing to cleanse properly can lead to clogged pores, breakouts, dehydration, and premature aging.
In addition, without proper cleansing, your other skincare products won't be able to penetrate the skin effectively, rendering them ineffective. Therefore, to maintain clear, healthy, and radiant skin, make sure to cleanse your skin twice a day using a gentle cleanser that suits your skin type
Moisturizing:
Moisturizing is a vital step in any skincare routine, especially in the realm of cosmetics. It helps to maintain the skin's hydration and elasticity, preventing dryness, flakiness, and irritation. When the skin is either too dry or too oily, it can lead to several common skin problems, such as acne. Therefore, choosing the right moisturizer is key.
For oily skin types, opt for a lightweight lotion rather than a heavy cream. Look for a moisturizer that contains exfoliating ingredients to help unclog pores and reduce excess oil. On the other hand, for dry skin types, creams are recommended as they contain higher oil content to deeply moisturize and nourish the skin.
Regular moisturizing can help keep your skin looking healthy, youthful, and radiant. Make sure to choose a moisturizer that is suitable for your skin type and apply it twice a day for best results.
Sun protection is extremely important for maintaining healthy skin and preventing various skin problems. The sun emits harmful ultraviolet (UV) radiation, including UVA and UVB rays, which can penetrate the skin and cause damage such as sunburn, premature aging, and even skin cancer.
So, applying sunscreen with a high SPF rating can significantly be one of the ways to reduce the risk of sun damage. It is recommended to use a broad-spectrum sunscreen that protects against both UVA and UVB rays, with an SPF of at least 30. Reapplying sunscreen every 2 hours, or after swimming or sweating, is also crucial for maintaining protection.
In addition to preventing skin damage, sun protection can also help to maintain a more even skin tone and prevent the development of age spots and other pigmentation issues. So, incorporating sun protection into your daily skincare routine is essential for promoting healthy, youthful-looking skin.
Click the link here for more information about sun protection: https://chloecosmetics84.wixsite.com/home/post/the-science-of-sunscreen
Whoahhhh, hold on tight! I know we've thrown a lot of info at you, but trust me, these basics are like the GPS for your journey into the magical world of cosmetics. The dermis layer is truly a marvel of nature, and we're excited to explore its many facets in greater detail.
Don't sweat the small stuff, and here are the key takeaways for this post and you'll be good to go. Check it out in Figure A1.4.
Figure A1.4. Key takeaways for memorization
And if you forget anything, just swing by my blog for a quick refresher. We've got you covered, literally.
Chloe.
References:
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(3) Bezerra, M. A., Santelli, R. E., Oliveira, E. P., Villar, L. S., & Escaleira, L. A. (2008). Response surface methodology (RSM) as a tool for optimization in analytical chemistry. Talanta, 76(5), 965–977. https://doi.org/10.1016/j.talanta.2008.05.019
(4) Birch-Machin, M. A., & Bowman, A. (2016). Oxidative stress and aging. British Journal of Dermatology, 175, 26–29. https://doi.org/10.1111/bjd.14906
(5) Cork, M. (1997). The importance of skin barrier function. Journal of Dermatological Treatment, 8(sup1), S7–S13. https://doi.org/10.3109/09546639709160948
(6) Kolarsick, P. A. J., Kolarsick, M. A., & Goodwin, C. (n.d.). Anatomy and Physiology of the Skin. SKIN CANCER, 12.
(7) Yousef, H., Alhajj, M., & Sharma, S. (2022). Anatomy, Skin (Integument), Epidermis. In StatPearls. StatPearls Publishing. http://www.ncbi.nlm.nih.gov/books/NBK470464/
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