Nail Science: Practice Questions & Explanations

The natural nail plate is technically called the onyx. The nail unit also includes the matrix (where nail cells are formed and the nail grows from), the lunula (the visible whitish half-moon at the base, which is part of the matrix showing through), the nail bed (the skin beneath the nail plate), the cuticle/eponychium (the skin around the nail base), and the free edge. Knowing the parts of the natural nail and their correct terms is core nail science tested on the cosmetology exam.

The natural nail grows from the matrix, the area of living tissue beneath the base of the nail where nail cells are produced. As new cells form, they push older cells forward, and these harden into the visible nail plate. Because the matrix is the growth center, damage to it can result in permanent nail deformity. The lunula is the part of the matrix visible through the nail as a pale half-moon. Understanding that the matrix is the source of nail growth is essential nail science.

If a client's nail or surrounding skin shows signs of infection — such as redness, swelling, pus, heat, or pain — the cosmetologist should not perform the nail service and should refer the client to a physician. Working on an infected area can worsen it and spread infection to tools, surfaces, and other clients. Diagnosing and treating infections is outside a cosmetologist's scope. Recognizing the signs of infection and knowing to decline service and refer is both an infection-control and a scope-of-practice requirement on the exam.

The lunula is the whitish, half-moon-shaped area visible at the base of the natural nail. It is actually the part of the matrix (the nail's growth center) showing through the nail plate. The free edge is the part of the nail that extends past the fingertip, the nail bed is the skin beneath the nail plate, and the cuticle is the dead skin overlapping the nail base. Identifying the parts of the nail unit by their correct names, including the lunula, is core nail science on the exam.

Healthy natural nails are made primarily of keratin, the same tough, fibrous protein that makes up hair and the outer layer of skin. The hardened keratin gives the nail plate its strength and protective quality. (Collagen and elastin are proteins of the dermis; melanin is the pigment that colors skin and hair.) Knowing that both nails and hair are composed largely of keratin is a basic but frequently tested fact connecting nail and hair science on the cosmetology exam.

The hyponychium is the slightly thickened skin directly beneath the free edge of the natural nail, where the nail plate separates from the fingertip. It helps form a protective seal that guards against infection entering under the nail. (The matrix is the growth center, the lunula is the visible part of the matrix, and the nail bed lies under the attached nail plate.) Knowing the parts of the nail unit, including the hyponychium under the free edge, is part of the nail-science content on the exam.