Anatomy and Physiology of the Hand, Arm, and Nail
What this domain tests
Anatomy items ask you to name nail structures and their functions, trace growth, and connect hand anatomy to safe service. Expect questions on bones, nerves, blood supply, skin layers, and contraindications.
Core rules
- The nail plate is dead keratin produced mainly by the matrix. The nail bed lies beneath the plate; the lunula is the visible portion of the matrix.
- The eponychium is the living proximal fold; the cuticle is the dead tissue at its edge. The hyponychium seals under the free edge; lateral folds and grooves guide the plate.
- Fingernails grow about 3–4 mm per month; toenails grow slower, about 1–1.5 mm per month. Growth slows with age, illness, and poor circulation.
- Hand bones: 8 carpals, 5 metacarpals, 14 phalanges. Key nerves are the median (thumb, index, middle), ulnar (ring, little), and radial (dorsal thumb/hand). The radial and ulnar arteries form the palmar arches.
- Skin has epidermis, dermis, and subcutaneous layers; glands and nerves lie in the dermis.
Worked example
A client has a horizontal ridge on one nail after a slammed drawer. You explain the injury likely damaged the matrix, so the ridge will grow out rather than disappear with buffing. Reasoning: the matrix forms the plate; localized matrix trauma creates a ridge, while nail-bed injury would more likely cause a bruise or separation.
Traps that cost marks
- Saying the nail grows from the nail bed.
- Treating the lunula as a separate organ rather than visible matrix.
- Calling the nail plate living tissue.
- Confusing the eponychium with the cuticle.