Anatomy and Physiology of the Skin
Anatomy and physiology questions test skin layers, cell types, glands, and barrier function. You need to connect structure to esthetic practice: why the epidermis does not bleed, why the dermis scars, and why the acid mantle matters.
Layers and cells
- Epidermis is avascular and keratinized. From deep to superficial: stratum basale, spinosum, granulosum, lucidum on palms and soles, and corneum.
- Keratinocytes produce keratin; melanocytes in the basal layer produce melanin; Langerhans cells are immune; Merkel cells are sensory.
- Dermis has papillary and reticular layers, with collagen, elastin, fibroblasts, blood vessels, nerves, hair follicles, sebaceous glands, and sweat glands.
- Hypodermis is subcutaneous fat for insulation and shock absorption.
Functions and barrier
- Skin protects, senses, regulates temperature, excretes, secretes, synthesizes vitamin D, and absorbs limited substances.
- The acid mantle, pH about 4.5 to 5.5, and intercellular lipids support the barrier. Over-exfoliation disrupts it.
Worked example
After gentle exfoliation, a client does not bleed. If a facial scrub causes bleeding, the esthetician has injured beyond the epidermis into the dermis, where blood vessels lie. Reasoning: the epidermis has no blood supply; dermal injury also raises scarring and infection risk.
Traps that cost marks
- Placing melanocytes in the dermis.
- Calling the stratum corneum living tissue.
- Confusing sebaceous oil glands with sudoriferous sweat glands.
- Saying the dermis lacks nerves.