Anatomy and Physiology of the Nail and Skin
Nail structures
Know the parts and their jobs. The matrix is the living tissue that produces the nail plate; damage here causes permanent distortion. The nail plate is the visible, non-living keratin structure. The nail bed lies beneath the plate and carries blood vessels and nerves, giving the nail its pink tone. The lunula is the whitish half-moon at the base - the visible portion of the matrix. The cuticle (eponychium) is the dead tissue seal at the base; the hyponychium is the seal under the free edge; the nail folds are the skin walls at the sides; the onychodermal band is the seal between plate and hyponychium.
Skin and growth facts
Nails grow roughly 3 mm per month on average, faster in summer and faster on the dominant hand; toenails grow more slowly. The nail plate is about 100 layers thick and absorbs water, which is why it swells and softens after soaking. Skin layers: epidermis (outer, no blood supply), dermis (nerves, glands, vessels), subcutaneous (fat).
Traps
Questions love confusing the matrix (living, produces) with the lunula (visible, not the whole matrix), and the cuticle (dead seal, never cut on a healthy nail) with the eponychium. Do not describe the nail plate as living tissue. Nail disorders such as onychomycosis, paronychia, and onycholysis are outside a technician's scope - recognize, do not treat, and refer.
Rule of thumb
"If it makes nail, it's matrix; if it seals, it's cuticle or hyponychium; if it's pink, it's bed."