Fundamental Skin Science

Skin Physiology: Key Milestones

Skin is the body's largest organ and the best-placed to inform us. It is organized into three layers: the epidermis on the surface, the dermis supporting it, and the hypodermis deeper down. At the outermost surface, the stratum corneum forms a protective barrier made of cells and lipids — the first line of defense against external aggressions.

Beneath this surface, the dermis houses blood vessels, nerve endings, hair follicles, and glands — sebaceous for sebum, sweat for perspiration. Together, these structures ensure the skin's major functions: protection, body temperature regulation, perception. The acid mantle, slightly acidic on the surface, contributes to the balance and comfort of healthy skin.

Knowing this anatomy changes the perspective on skincare. A cosmetic product primarily acts on the superficial layers of the epidermis: it helps maintain hydration, support the appearance of the barrier, and surface comfort, without claiming to replace the skin's natural functions.

On the program

This module consists of the following chapters:

• Intelligent Skin Anatomy
• Epidermis, Dermis, and Hypodermis
• The Skin Barrier
• The Hydrolipidic Film
• The Skin Microbiome
• Skin pH
• Cell Renewal
• Sebum and Lipid Balance
• Visible skin aging
• Skin hydration

Quick Glossary

Skin

The body's largest organ and the primary interface with the outside world; its surface, the epidermis, plays a visible role in protection and comfort.

Cells

The basic building blocks of the skin; in the stratum corneum, they assemble with lipids like bricks and cement.

Epidermis

The outermost layer of the skin, in contact with the air; it houses the skin barrier which helps preserve surface hydration.

Dermis

The layer beneath the epidermis, rich in collagen and elastin, which supports the visible firmness and elasticity of the skin.

Protection

All the actions that help the skin defend itself from external aggressors, first and foremost sun protection.

Concepts also covered

This chapter also sheds light on: body · organism · barrier · function.

Key takeaways

• Start with your actual skin: observe its skin and comfort before multiplying products.
• A simple and regular routine, adapted to your profile, is better than accumulating treatments.
• Read formulas and promises with discernment: this content gives you benchmarks, not prescriptions.

Educational cosmetic content, for informational purposes. It does not replace dermatological advice.