Skin Anatomy, Physiology, and Wound Healing
This domain tests skin layers, pigment placement depth, and the healing timeline-facts you need to predict retention and avoid scarring.
Structure
- Epidermis: stratum corneum, granulosum, spinosum, basale; avascular keratinocyte barrier. Melanocytes sit in the basale layer.
- Dermis: papillary (upper, loose) and reticular (deeper, dense collagen/elastin); contains nerves, blood vessels, glands.
- Hypodermis: fat and connective tissue; not a tattoo target.
Permanent cosmetics belong in the upper papillary dermis, often about 0.5–1 mm deep depending on site and skin thickness. Too shallow and pigment sheds with the epidermis; too deep and you cause bleeding, bruising, blowout, or scarring.
Healing
Hemostasis occurs in minutes to hours; inflammation peaks in days 1–3; proliferation runs roughly days 3–21; remodeling continues up to 12 months. Epidermal turnover is about 28 days, so the “peeling” phase is normal. Final color is judged after 4–6 weeks.
Worked example
A client has very oily eyelids and asks for a crisp liner. Oily skin and thin eyelid epidermis can reduce retention and increase irritation. The reasoned plan is conservative pressure, a smaller needle, and a scheduled touch-up-not more passes in one sitting.
Traps
Saying pigment lives in the epidermis permanently; claiming the dermis has no blood vessels or nerves; treating scab removal as harmless; assuming every client heals on the same schedule.