What is Skin – The Basics

Nature gives you the face you have at twenty; it is up to you to merit the face you have at fifty” – Coco Chanel

I remember the day we learned about skin in our 7th grade science class. I was pretty amazed and maybe a little grossed out to learn that it is our body’s largest organ and is constantly renewing itself by shedding dead skin cells and generating new ones every 4 weeks. Neat. But, there’s a lot more that we need to know about skin if we want to try and make it look its best.  This post covers the very basics.

Skin – The Basics

Skin is composed of 3 layers.


The epidermis layer

This outer layer is responsible for making new skin cells, giving skin its color through production of melanin by a special type of cell called a melanocyte (melanin protects us from sun’s harmful UV rays), and protecting the body. This layer is mostly made up of dead skin cells called keratinocytes which produce keratin to form a protective barrier against environmental damage. New cells are made at the bottom of the layer and move up to the surface within 4 weeks where they harden and then shed.

The thickness of the epidermis level varies based on where it is on the body. As a point of reference, the skin on your eyelids is < .1mm versus the skin on your palms and soles of your feet which has the thickest epidermal layer, measuring ~ 1.5mm.

As we age, the cell turnover process declines, i.e. the rate at which old cells are sloughed off and are replaced by new cells slows down (the rate of keratinocyte proliferation declines 30% to 50% between the ages of 30 and 80). This decrease in the natural shedding of skin results in a dull appearance and rough texture. There is also a decrease in melanocytes, leaving the remaining melanocytes left with having to create more pigmentation or color to make up for the loss. This decline in cell turnover also results in naturally drier skin. In addition, as we age, the epidermis layer thins by about 5% to 30% by age 60.  Yikes!!

The dermis layer

The middle layer, the dermis layer, serves several functions including: making sweat (there are tiny sweat glands in this layer that make sweat and come out of holes that poke through the epidermis layer called pores), helping us feel things via nerve endings found in this layer, growing hair (the dermis layer contains the root of each hair on our skin), making oil (another gland found in this layer is responsible for making oil which keeps skin soft, smooth, and waterproof), and lastly bringing nutrients and oxygen from the blood into cells.

This layer is made up elastin and collagen which make the skin strong and robust while at the same time stretchy (elastin allows skin to be elastic, pliable and firm, and collagen makes it plump). Now I get this fad around collagen ingestibles…kinda.

This layer is also where you find the majority of hyaluronic acid which acts as a filler, helping to keep fine lines and wrinkles at bay (btw, nearly 50% of hyaluronic acid in the body is found in the skin). However, what hyaluronic acid is most popularly known for is its ability to maintain hydration in the skin because it is able to hold up to 1,000 times its weight in water! This helps keep the skin plump, moist, soft, and smooth and also helps reduce the appearance of fine lines and wrinkles.

The majority of age-related changes occur in the dermis layer which can lose 20% to 80% of its thickness during the aging process. This is the result of collagen, elastin, and hyaluronic acid being produced at a slower rate and the natural process of glycation, in which sugar molecules bind to proteins such as collagen and degrades their functionality.

The subcutaneous layer

This is the deepest layer and it is mostly made up of fat and connective tissue. This layer acts as an insulator and helps regulate body temperature.

Over time, this layer also starts to lose its fat cells, losing its volume, which helps explain why we become more prone to injury and bruises, i.e. less padding to protect our muscles and bones.


Our skin is a very complex organ. Key things to remember is that over time its cell renewal process takes longer which means the rate at which we get “fresh” skin decreases as we age, the layers begin to thin out which exposes more at the surface of the skin (this probably helps explain why we get dark circles under our eyes as we age), and there are key cell structures whose production decreases over time that we may be able to supplement either topically or through some type of ingestible.


Cellbone. “Hyaluronic Acid & Aging Process”.
Consultant (December 2011). “Skin Disorders in Older Adults:  Cutaneous Signs of Normal Aging”. Volume 51, Issue 12.
Farage, M. A., Miller, K. W., Elsner, P., & Maibach, H. I. (2013). “Characteristics of the Aging Skin”. Advances in Wound Care2(1), 5–10.
Howard, D. Dr.  “Structural Changes Associated with Aging Skin”.
Kolarsick, P. A. J., Kolarsick, M. A, Goodwin, C.  “Anatomy and Physiology of the Skin”.
Papakonstantinou, E., Roth, M., & Karakiulakis, G. (2012). “Hyaluronic acid: A key molecule in skin aging”. Dermato-Endocrinology4(3), 253–258.
PubMed Health. “How does skin work”.
Sator, P.  (Mar 2006).  “Skin Treatments and Dermatological Procedures to Promote Youthful Skin”
Skinspirit (July 2013).  “What is Hyaluronic Acid?”.
The American Academy of Dermatology. “The layers of your skin”.


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