🎓 Epidermis: Outermost layer of skin


Functions of the Epidermis

  • Maintain and regulate water content of the skin
  • Provide antioxidant barrier and immune protection for the body
  • Synthesize vitamin D
  • Provide skin color
  • Turn over new skin cells


  • Human skin consists of 2 main layers, Epidermis & Dermis
  • Beneath the Epidermis and Dermis, is a third layer, the Hypodermis, which is mostly fat cells
  • The Epidermis is the protective outer layer of skin, which is composed of 5 layers:
    • Stratum Corneum: “Horny Layer” of water-resistant dead cells called corneocytes and lipids, together which help form what is often referred to as “brick and mortar” structure, where dead cells are the bricks and lipids are the mortar. The Stratum Corneum is the thickest of the epidermal layers and is embedded in lipids which are made of ceramides, cholesterol, and fatty acids. This lipid matrix waterproofs the epidermis, preventing dehydration and providing moisture permeability.
    • Corneocytes contain a blend of hygroscopic (water loving) compounds which are referred to as Natural Moisturizing Factor (NMF) which keeps the skin hydrated in the Stratum Corneum. NMF can be washed away by soaps, which reduces the skin’s barrier function, causing it to become dry, flaky, and uncomfortable
    • Stratum Lucidum: Translucent layer of dead cells
    • Stratum Granulosum: Cells begin to die in this layer
    • Stratum Spinosum: Responsible for lipid and protein synthesis
    • Stratum Basale: This is where new skin cells, called keratinocytes, are formed and pushed upward through the layers of the epidermis to create new skin (keratinization). As the cells move through the layers, they change their shape and composition as they move upward, becoming less permeable until they reach the Stratum Corneum where they are finally dead cells, and are eventually shed from the skin’s surface. The process of turning over new cells is called desquamation, and takes approximately 4 weeks to uncover new skin.
      Melanocytes are found in the Basale layer and produce melanin, which is a pigment that gives our skin its color.

  • Vitamin D production occurs in the epidermis. Because African American skin absorbs more UVB light than Caucasian skin, it requires 3-5 times longer exposure to make the same amount of vitamin D as Caucasian skin.
  • The epidermis does not contain blood vessels, it relies on the dermis for nutrients.
  • Bathtub water is a hypotonic solution (concentration of solutes is greater inside the cell than outside of it) and your skin will absorb water through osmosis. The ocean is a hypertonic solution (concentration of solutes is greater outside the cell than inside it) and over a long period of time your skin can lose water through a reversed osmotic flow.


Very interesting. I guess this, “Vitamin D production occurs in the epidermis. Because African American skin absorbs more UVB light than Caucasian skin, it requires 3-5 times longer exposure to make the same amount of vitamin D as Caucasian skin,” explains why I’ve met so many African American women who are Vitamin D deficient. I always wondered why that was an issue with them.


I’ve had African American colleagues who would use tanning booths.They said they were using them because
it gave them a healthier look after working in a sales room all day. I wonder if it gave them enough of a Vitamin D benefit?


Very interesting… I had no idea that it took 4 weeks for fresh, new skin to replace all the old dead skin. Is this why so many women get chemical peels? Maybe they don’t want to wait the 4 weeks for their skin to turnover. I know that the purpose of them are to help reveal more radiant skin. I’ve never done any sort of chemical peel, I’ve always thought it looked so harsh.


Emgie, this is what I found on SkinCancer.org, “A tanning bed will never provide you with the vitamin D that you need, nor is it safer than tanning outdoors. … But it is UVB (the sun burning rays) — not UVA — which helps the skin make vitamin D, so you are increasing your risk of skin cancer without receiving any benefit!”


Wow, great to know about tanning beds!
Our pediatrician gave us vitamin D drops for our daughter, I’m guessing it’s a best practice nowdays?


According to vitamindcouncil.org that was a necessary decision by your pediatrician. :+1:t4:“Summary. The two main ways to get vitamin D are by exposing your bare skin to sunlight and by taking vitamin D supplements. You can’t get the right amount of vitamin D your body needs from food. The most natural way to get vitamin D is by exposing your bare skin to sunlight (ultraviolet B rays).


This information seems contradictory to the Tanning Bed Information in relation to UVA or UVB. This seems more understandable, from skincancer.org, “Our bodies manufacture vitamin D when the sun’s ultraviolet B (UVB) rays interact with 7-dehydrocholesterol (7-DHC) present in the skin. “However, we can produce only a limited amount of vitamin D from UVB. A few minutes at midday are sufficient for many Caucasians,” says Roy Geronemus, MD, clinical professor of dermatology at New York University Medical Center and director of the Skin/Laser Division at the New York Eye &amp: Ear Infirmary. "After reaching the production limit, further exposure actually destroys the vitamin, decreasing vitamin D levels."Furthermore, UV exposure is unlikely to produce enough vitamin D in darker skin, so African-Americans and dark-skinned Hispanics relying on UV alone are especially at risk for deficiency. The National Institutes of Health’s Office of Dietary Supplements also warns that the elderly have a reduced ability to synthesize vitamin D from sunlight: and between November and February, UV radiation (UVR) is insufficient to produce vitamin D in people living above 42 north latitude, which includes Boston, northern California, and other areas north.”


It’s been a long time since we’ve seen each other. I hope for their sake they’ve discovered this info on their own.


Thanks for sharing all that great info.


Thank you for all the GREAT Vitamin D information! Another critical purpose of the skin is to eliminate waste. This is often the reason for body odor and some acne. I’ve found since I’ve started eating and using all organic and natural that I no longer need deodorant. Previously before removing toxins from my environment and body, I often had to apply deodorant 2x a day and only found two to even work. Our skin is often the first indicator of our overall health. And when considering different skin problem it is important to consider what role our internal health may be playing.


I remember learning about the layer of your skin in school and I always found it interesting how many layers there are.


thank you for sharing.


Fascinating stuff! Vitamin D deficiency is extremely common these days with our indoor lifestyles,
and can lead to some serious problems! Good reason to get outside and get some sunshine!! I try to get at least 10 to 15 minutes a day of direct sun.


I’ve noticed when I don’t drink enough water or if I’m eating a lot of junk food or drinking too much alcohol my skin looks kind of dull and/or I get breakouts in places I don’t normally break out. I’ve heard of people who eat a lot of sulfury type foods (like onions and garlic) having a stronger body odor because it is coming out through the skin. Essentially they are “sweating it out”.


Almost everyone I know is vitamins d deficient, including myself.

I take prescribed 50,000 IU of vitamin D a week.
I spend time outdoors, but I also use sunscreen to protect my skin.
Is the use of sunscreen (promoted so widely the past decade or so) causing vitamin D deficientcies?


Great question.
https://www.skincancer.org/healthy-lifestyle/vitamin-d/damage"… it doesn’t take much sun exposure for the body to produce vitamin D. Even committed proponents of unprotected sun exposure recommend no more than 10 to 15 minutes of exposure to arms, legs, abdomen and back, two to three times a week, followed by good sun protection.20
That minor amount of exposure produces all the vitamin D your body can muster."“You can acquire vitamin D from a combination of diet and supplements. Fatty fish such as salmon, mackerel and tuna are especially good sources. Small amounts are also present in egg yolks, beef liver and cheese. And many common foods such as milk and orange juice are fortified with vitamin D.”


I get so worried about sun damage that I often deglect my vitamin D production.
I’m loving all the tips on how to fight vitamin D deficiency


Great information.
However, I abused tanning beds in my younger years.
As far as vitamin D I was diagnosed several years ago being very low and Dr had me bump up my intake.
I love learning about skin and how it all works together.
I am a huge Retina user and believe in exfoliating to help my skin do the turnover.
I’m always wanting that dead skin layer gone so my products can work better and faster.


My mother’s doctor who did a study on vitamin D deficiency in women recommended they take 10,000-25,000 IU a day. I noticed that taking at least 5,000 IU has completely reversed the tooth sensitivity I was having. For cancer patients, more is essential. With all the pollution, it’s really no wonder so many people are deficient. I think more people should consider having a sun room/porch for all the benefits of sunshine.