Understanding Your Skin

Take a journey into the layers of your skin and uncover the science behind its structure and function. Explore how it protects and adapts every day.

The Layers of Your Skin

Epidermis (Outermost Layer)

Stratum Corneum: The most superficial layer contains cells with thick, waterproof membranes. There are few desmosomes (adhesive proteins) holding them together, allowing easy shedding and marking the end of keratinization.
Stratum Lucidum: In this layer, keratinocytes have lost their nuclei and have indistinct borders. It is typically a very thin layer, often visible only under a microscope in areas of thick, hairless skin.
Stratum Granulosum: Here, keratinocytes are filled with keratohyalin granules that bind keratin filaments together. This layer also produces lipid-rich lamellar bodies, enabling the skin's waterproofing.
Stratum Spinosum: In this layer, keratinocytes begin keratinization, filling with keratin (a structural fibrous protein) as they transition into fully differentiated cells. The process, from cell birth to shedding, is debated but typically takes around 30 days.
Stratum Basale: The deepest epidermal layer generates keratinocytes through constant mitosis. Keratinocytes make up about 90% of epidermal cells, while others include melanocytes (UV protection), Langerhans cells (immune function), and Merkel cells (touch receptors).
Basement Membrane: A functionally active extracellular matrix that anchors the epidermis to the dermis.

Dermis

The dermis provides structural support, elasticity, and nourishment through its fibrous connective tissues, including collagen and elastin, which are organized into Langer's lines.
It also contains blood and lymphatic vessels, nerves, and sensory receptors, along with hair follicles, arrector pili muscles, sebaceous glands, and sweat glands. All of which are essential for temperature regulation, hydration, and sensation.

Subcutis (Fat Layer)

The subcutis is a layer of loose connective tissue between the skin and muscle fascia, containing white adipose tissue for insulation, energy storage, and protection.
It also includes small tendons from underlying muscles to aid in movement and varies in thickness depending on the amount of fat present.

How Your Skin Works

Protection and Immune Defense

The skin acts as a shield, protecting the body from physical injury and harmful pathogens like bacteria and viruses. It serves as a physical barrier and utilizes immune cells such as Langerhans cells, which destroy invaders and can travel through the body to alert the secondary immune system to respond to threats. Additionally, the skin protects against UV radiation through melanocytes, which produce melanin to safeguard the DNA of other cells from UV damage.

Temperature Regulation

The skin plays a key role in temperature regulation. In cold environments, the skin constricts capillaries in the dermis to retain heat and tightens arrector pili muscles, causing hair to stand up and form an insulating layer. In hot conditions, capillaries dilate, and sweat glands are activated to cool the body by evaporating sweat, releasing heat from the skin. Thermal receptors present can detect heat and send signals to the central nervous system. This triggers reflexes to remove the skin from harmful temperatures and warns the brain to avoid those conditions.

Sensation and Wound Healing

The skin detects pressure through mechanoreceptors, pain via nociceptors, and temperature through thermoreceptors, enabling the body to respond to a wide range of stimuli. When the skin is injured, the wound healing process begins with inflammation, attracting immune cells to sterilize the area by removing pathogens and dead tissue. This is followed by the proliferation of new cells and their gradual remodeling into the correct structure, restoring the skin's integrity.

Anatomy of Nails

Nails are an extension of the skin and are made of keratinocytes, just like the skin. They serve various functions, including sensation, acting as tools, providing protection for the fingertips, and serving as ornaments.

Nail Plate: The hard, visible part of the nail made of dead keratinocytes.
Free Edge: The white tip of the nail that extends beyond the nail bed and is not attached to it.
Nail Root: Hidden under the skin, this is the part you can't see, where the nail begins.
Nail Bed: The visible pinkish part of the nail that lies beneath the nail plate.
Germinal Matrix: Surrounds the nail root and is responsible for producing new nail cells. It can extend to the nail plate and is sometimes visible as the lunula (the "half-moon" shape) is a visible part of this matrix.
Proximal and Lateral Folds: Skin bordering the nail at the base and round the sides.
Perionychium: Tissue that attaches the nail to the proximal and lateral folds creating a seal.
Cuticle: A thin, transparent layer produced by part of the perionychium to seal and protect the nail.