While you see and feel your skin surface everyday, its intricate five-layer structure is always hidden from your naked eye. When you apply products to your skin, you’re mainly interacting with the stratum corneum. It’s the outermost layer of your skin, so it’s the only thing between your body and all that surrounds it.
Although it’s a paper-thin accumulation of dead skin cells (which you’ll get to know shortly), the stratum corneum is incredibly alive. With its genius architecture, its a security guard you can count on.
Out of the many threats it keeps out, here are few big ones:
Now, let's imagine your body as a brick house.
The structure of cells within the stratum corneum even resembles a brick wall! Looking closer, we can see a harmonious brick and mortar pattern.
In this model, the bricks represent corneocytes.
To understand what corneocytes are, let’s take a quick look at their life story:
They start out as keratinocytes, a fancy term for cells that get produced deep within the skin. They travel toward the surface of the skin and after going through multiple transformations, they join the top layer as flattened, dead skin cells: corneocytes. So, now that you’ve met the “bricks”, let’s move on to the “mortar.”
The “mortar” between the bricks is made of lipids.
These molecules can’t be dissolved in water, and we usually associate them with fats. They are packed tightly around the “bricks” in repeating patterns creating a real cement. When it comes to protection, the lipids are the stars of the show. Their toughness actually makes them a big part of your body’s defense! Here, we see a powerful trio of lipids: Ceramides, Fatty Acids, and Cholesterol.
An optimal natural protection.
The bricks and mortar work together as your skin’s little gatekeepers, deciding which molecules can enter and exit the skin. They make sure your skin retains what it desperately needs, water especially, while keeping out toxins and other harmful particles.
Environmental threats like pollution and changing weather, as well as harsh ingredients in products can mess with the balance of lipids in your skin’s wall. When there’s a lack of mortar, your wall can lose some of its structural integrity. This is not happy news for your skin.
With a compromised barrier, our skin can lose water rapidly, leaving it dry and itchy. As a wall’s structure becomes more chaotic, irritants can sneak through more easily and harm our skin. Today, products in the cosmetics industry are often filled with unfamiliar ingredients, and we are encouraged to apply them generously.
No more secrets.
We’ve been in the dark about how ingredients interact with our skin for too long. At Elsi, we’re here to empower you with the science of your skin. Today, we learned about the built-in genius of the stratum corneum. It’s here to protect us, so why not help it thrive?
Let’s get to know how our skin works, starting with the stratum corneum, to make intuitive decisions about its care. Only then can we nurture our skin and create an optimal balance.
by Mariana Giraldo, Mechanical Engineering student .
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GP Menon et al., 2012
The structure and function of the stratum corneum
E Jungman et al, 2012
Development of a percutaneous penetration predictive model with chromatographic and spectroscopic tools (On penetration of the skin)
K.R. Feingold, C. Grunfeld, 2018
Introduction to Lipids and Lipoproteins
K.R. Feingold, P.M. Elias, 2014
Role of lipids in the formation and maintenance of the cutaneous permeability barrier