When people think of the skin, they often think of the appearance, the smoothness, the glow and maybe a few wrinkles here and there. When people talk about skincare, they usually think about products such as, cleansers, serums, and the latest craze “anti-aging creams.”
As a pathologist, when I view skin through a microscope, I see something much deeper. A complex, layered organ, working quietly every day to protect us from the damaging effects of bacteria, viruses, fungi, pollutants and other irritants. One of the fascinating and complex organs is skin. It is one of the few organs can see from the outside and yet most people do not realize how complex and important it is.
Your skin is not just a covering. It is a living, working organ made up of multiple layers of different kinds of specialized cells, glands and blood vessels designed to protect, regulate and respond to the world around us. Here are a few important facts that you should know about your skin:
It is your largest organ.
Makes up 13% of your body weight.
You lose between 50-70 million dead skin cells each day.
Your skin renews cells approximately every 28 days, but this cycle slows with age.
Let us take a closer look at what your skin looks like under the microscope.
Layers of your skin from outside in
1. Epidermis
2. Dermis
3. Subcutaneous tissue
Let us take closer look at what’s inside of these layers
Epidermis
The epidermis is the most outer layer. It has several sub-layers. The most outward of the sub-layers is the Stratum Corneum, the shedding layer. It is constantly renewing itself between 28 to 40 days. This process is called epidermal turnover. This is your body first line of defense.
- It consists of cells called keratinocytes laying on top of each other, layer upon layer. Think of them as bricks lying on top of each other. These are mostly dead cells and have a lot of keratin and tightly packed.
- These cells that eventually flake off.
What keeps the keratinocytes bound together?
These are mainly three components that do that. They form the mortar between the bricks.
They are
LIPIDS- such as ceramides, cholesterol and free fatty acids
PROTEINS – form the tight junctions between keratinocytes.
NATURAL MOISTURIZING FACTORS- very tiny molecules that attract and hold water.
In addition to forming a protective shield, keratinocytes have other functions. For example, keratinocytes that are living in the deepest layers of epidermis synthesize vitamin D using energy from sunlight.
Other important cells in the epidermis are
Melanocytes cells that produced melanin for sun light protection and skin pigment,
Immune cells and Langerhans cells which are involved in inflammation, wound healing.
Main functions of the epidermis
Keeping your cells moist (hydrated)
Forming a protection barrier which prevents pathogen entry.
Resist microbial growth.
Protects against attack from bacteria, viruses, fungi, irritants, pollution and allergens.
2.THE DERMIS- the middle layer
This thick layer lies under the epidermis and has important structures.
SKIN GLANDS
1. Oil (sebaceous glands) are attached to hair follicles and secrete an oily substance called sebum that moisturizes the skin and hair.
2. Sweat glands help regulate body temperature
3. Ceruminous glands produce ear wax.
4. Mammary glands – produces milk at childbirth.
The dermis also has blood vessels, lymphatic vessels, nerves, hair follicles, collagen and elastin fibers (provide strength and elasticity).
3- SUBCUTNEOUS TISSUE – the deepest layer
This layer lies under the dermis and has important structures.
1. Adipose tissue (fat) which stores energy, provides insulation and cushions the body
2. Nerves which senses pressure and vibration.
3. Blood and lymphatic vessels bring oxygen and nutrients to skin cells, remove waste helps with temperature regulation.
4. Smooth muscle and collagen fibers
5.Loose connective tissue that connects the skin to muscle and bones.
The journey of a skin cell
A new keratinocyte is formed in the bottom (basal) layer
It slowly migrates upward through the five layers of the epidermis
During this journey, which takes the cell about 28–40 days, it gets filled with keratin, loses its nucleus (its headquarters where DNA is stored), dies and becomes a flat, tough cell in the stratum corneum and finally, the cell sloughs off as a dead skin particle.
Why shedding matters
- Removes damaged or old cells
- Protects against infection and dehydration
- Keeps skin smooth and resilient
- Plays a role in skin tone and texture
The next time you apply your cream, remember you’re not just moisturizing, you are communicating with your skin’s biology, encouraging every cell to perform its optimal function.
As a pathologist, I see beauty as a reflection of cellular health. When we nourish the skin with pure ingredients such as natural lipids, antioxidants, and healing botanicals we support its innate ability to repair, renew, and protect.
Julietta Fiscella M.D. CPE, FCAP.