CLS Skin Anatomy and Fitzpatrick Scale

Question 1

The epidermis is divided into five layers. Which layer is directly responsible for producing new skin cells through mitosis?

Accepted Answer

Stratum basale

Answer

The stratum basale (basal layer) is the deepest epidermal layer and contains mitotically active keratinocytes and melanocytes. New keratinocytes produced here migrate upward through the other layers, maturing and eventually becoming the anucleate corneocytes of the stratum corneum.

Question 2

What is the primary function of melanin in skin?

Accepted Answer

Absorbing and dissipating UV radiation to protect underlying cells from DNA damage

Answer

Melanin is produced by melanocytes in the stratum basale and transferred to surrounding keratinocytes. It forms a supranuclear 'cap' over the nucleus, absorbing UV radiation and converting it to heat, thereby protecting cellular DNA from UV-induced mutagenic damage.

Question 3

Which Fitzpatrick skin type is characterized by skin that 'always burns, never tans' and is associated with the highest risk of UV-induced damage?

Accepted Answer

Type I

Answer

Fitzpatrick Type I describes very fair skin, often with red or blonde hair and blue or green eyes, that always burns upon sun exposure and never develops a protective tan. This type has minimal melanin and the highest susceptibility to UV-induced erythema and photodamage.

Question 4

Where are hair follicles located anatomically, and why does this matter for laser hair removal?

Accepted Answer

Rooted in the dermis (bulb in the deep dermis, bulge in the mid-dermis); laser must penetrate to dermal depth to destroy the follicle

Answer

Terminal hair follicles are rooted in the dermis, with the bulb at depths of 2–7 mm. The follicle bulge (stem cell niche) is located at approximately 1–1.5 mm depth. Effective laser hair removal requires sufficient fluence at these dermal depths, which depends on wavelength selection (longer wavelengths penetrate deeper) and adequate energy delivery.

Question 5

Which statement correctly describes the difference between eumelanin and pheomelanin?

Accepted Answer

Eumelanin is brown-black and absorbs laser energy efficiently; pheomelanin is yellow-red, found in red and blonde hair, and absorbs laser energy less efficiently

Answer

Eumelanin is the dark brown-to-black pigment that strongly and broadly absorbs laser wavelengths, making it an effective chromophore for laser hair removal and pigmentation treatments. Pheomelanin is the red-to-yellow pigment in red and blonde hair and lighter skin tones, with lower and less broad laser absorption, explaining why light hair is poorly targeted.

CLS - Certified Laser Specialist Practice Test

CLS - Certified Laser Specialist Practice Test

CLS Skin Anatomy and Fitzpatrick Scale