The Biology of Skin: Understanding Its Structure and Function

Published on 23 October 2025 at 10:16

Explore the layers of the skin, their functions, and how they contribute to overall health.

 

As we were taught in school, the skin consists of three layers: the epidermis, dermis, and hypodermis. Interestingly, the largest organ of our body is the skin, which acts as a shield against external factors to protect other organs. My teacher once mentioned that the majority of the dust in our homes consists of dead skin cells. Did I believe it initially? Not at all, until I learned more about the skin.

 

So let's talk about first layer, which is the epidermis.

 

Overview of the Epidermis

The epidermis is the outermost layer of the skin and serves as a protective barrier for the body. It is primarily composed of keratinocytes, which produce keratin, a protein that helps protect the skin from damage and water loss.

Layers of the Epidermis

The epidermis is typically divided into five distinct layers, each with specific functions:

 

  • Stratum Corneum: The outermost layer, composed of dead keratinized cells that provide a tough barrier against environmental damage.

    Fun story: Many therapists try to explain to clients using this term "Stratum Corneum" during consultations, without simplifying it to just being the top layer of skin.

  • Stratum Lucidum: Found only in thick skin areas (like the palms and soles), this thin layer provides an additional barrier and is not present in thinner skin.

  • Stratum Granulosum: This layer contains granules that help in the process of keratinization, where keratinocytes begin to die and lose their nuclei, becoming more flattened.

  • Stratum Spinosum: Composed of several layers of keratinocytes that appear spiny due to desmosomal connections, this layer provides strength and flexibility to the skin.

  • Stratum Basale: The deepest layer, where new keratinocytes are generated. It also contains melanocytes, which produce melanin, contributing to skin color and protection against UV radiation.

    Interesting fact: This layer plays essential roles in terms of regeneration and melanin production. Most of our professional peels in the treatments are designed to target the Stratum Basale of skin.

 

Functions of the Epidermis

The epidermis serves several essential functions, including:

 

  • Protection: Acts as a barrier against pathogens, chemicals, and physical injuries.

  • Water Regulation: Helps prevent excessive water loss from the body.

  • UV Protection: Melanin produced by melanocytes provides some protection against harmful ultraviolet radiation.

    Interesting fact: Producing Melanin is actually a protective mechanism of the skin against UV.

  • Sensory Reception: Contains nerve endings that allow for the sensation of touch, temperature, and pain.

    This is why clients would feel tingly, warm and prickly when using medical-grade products and professional peels.

  • Vitamin D Synthesis: Plays a role in the production of vitamin D when exposed to sunlight.

    Interesting fact: Statistics have shown that 23% Australian adults are deficient in vitamin D. Source Australian Health Survey: Biomedical Results for Nutrients, 2011-12

 

The epidermis is vital for maintaining the overall health and integrity of the skin, making it a crucial component of the integumentary system.

 

Picture's source: https://www.researchgate.net/figure/Schematic-representation-of-epidermis-layer-of-human-skin_fig3_348644834

Overview of the Dermis

If we think of epidermis as a shield for our skin and body, then dermis would be a brain to perform the functions. Imagine like springs in the mattress, if there are good springs, the mattress would be more bouncy and firm to support our body.

Layers of the Dermis

There are two main layers in the dermis:

  • Papillary layer (Upper dermis): - Thin and superficial layer, just beneath the epidermis
    - Made of loose connective tissue
    - Contains capillaries, sensory nerve endings, and dermal papillae (which form fingerprints)
    - Provides nutrients to the epidermis and helps regulate temperature
  • Reticular layer (Deeper dermis):- Thicker and deeper layer
    - Made of dense irregular connective tissue with collagen and elastin fibers
    - Provides strength, elasticity, and structure to the skin
    - Contains hair follicles, sweat glands, sebaceous glands, and larger blood vessels

The fact is, as we age every sing year, we are loosing about 1% of collagen production not even mentioning about other factors like sun damage, stress, diet, medication, smoking and alcohol. So it could be more than 1% each year if we do not look after our health.

Collagen and Elastin?

Collagen, simply is a big and complex protein that forms the skin structure. This is 80% dry weight of our skin. When we loose collagen, we start having fine lines and wrinkles. But Elastin is very different from Collagen, makes up about only 2% the weight of our skin, works like springs in mattress, push everything back with the resistance. When we smile or having expressions, Elastins helps to bring the skin back to normal without having wrinkles. 

 

 

 

 

 

 

Source: https://www.enhance-me-training.com/topic/the-dermis/

Overview of the HypoDermis

It is also called as subcutaneous layer. This lies below the dermis, made of connective tissues and fat cells that acts like a cushion protect underlying muscles, organs and bone from impact. 

This layer helps to insulate the body temperature, protect other parts of body, store fat as reserve energy, and anchors the skin with the muscles and bones.

There are large blood vessels, lymph vessels and nerves in the hypodermis.

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