Anatomy and Physiology of the Skin
What this domain tests
Anatomy questions focus on skin layers, cell types, glands, and the barrier. You need to connect structure to treatment effects and contraindications.
Core rules
- Epidermis is avascular and renews from the stratum basale. Keratinocytes make keratin; melanocytes make melanin; Langerhans cells are immune; Merkel cells sense touch.
- The dermis contains collagen, elastin, blood vessels, nerves, hair follicles, sebaceous glands, and sweat glands. It supplies the epidermis.
- The hypodermis, or subcutaneous layer, stores fat and insulates.
- The acid mantle is a slightly acidic film of sebum and sweat that supports barrier function and limits some microbes.
- Exfoliation and most facial products act on the epidermis. Aggressive treatment can damage the barrier; deep wounding is outside esthetic scope.
- UV exposure damages DNA, collagen, and elastin; it drives photoaging and skin cancer risk.
Worked example
A client asks why an exfoliating acid makes skin smoother but does not remove a deep scar. Reasoning: superficial acids accelerate shedding of epidermal cells; a deep scar involves dermal collagen, which esthetic products do not rebuild.
Traps
Saying the epidermis contains blood vessels; placing sebaceous glands in the epidermis; confusing melanin with keratin; promising dermal remodeling from a superficial facial.