Final answer:
The tracks you refer to are likely the structures surrounding the nail bed and nail plate that aid in nail growth, such as the nail matrix, nail root, and nail fold.
Step-by-step explanation:
When you're asking about the "tracks" through which the nail moves as it grows, you're likely referring to the structures surrounding the nail bed and nail plate. The nail itself is part of the integumentary system and is a keratinous structure that begins its growth from the nail root, which is lodged deep in the epidermis at the proximal end of the nail. The nail matrix, which is a part of the nail bed, is crucial as it contains the stem cells that divide and enable the nail to grow.
The nail plate is the visible part of the nail that overlays the nail bed. As the nail grows, cells from the matrix multiply and push the older cells towards the fingertip, elongating the nail plate over the nail bed. The nail fold helps to anchor the nail plate on the sides of the nail and the cuticle or eponychium seals the edges of the nail plate to minimize the risk of infection. Moreover, the nail bed beneath the nail plate is rich in blood vessels, which gives it a pinkish appearance, except for the crescent-shaped lunula.
The lateral nail fold overlaps the nail body on the sides, hence it plays an essential role in anchoring the nail to the finger. The hyponychium is found beneath the free edge of the nail plate, further from the cuticle, and is a thickened portion that also contributes to the structural integrity of the fingertip.