There is a rich arterial blood supply to the nail bed and matrix derived from paired digital
arteries (Figure 1.2). The main supply passes into the pulp space of the distal phalanx
before reaching the dorsum of the digit. The volar digital nerves (Figure 1.2c) are
similarly important in providing nerves to the deep nail apparatus structures. An
accessory blood supply arises further back on the digit and does not enter the pulp space.
There are two main arterial arches (proximal and distal) supplying the nail bed and
matrix, formed from anastomoses of the branches of the digital arteries. In the event of
damage to the main supply in the pulp space, such as might occur with trauma, infection
or scleroderma, there may be sufficient blood from the accessory vessels to permit
normal growth of the nail.
There is a capillary loop system to the whole of the nail fold, but the loops to the roof
and matrix are flatter than those below the exposed nail. There are many arteriovenous
anastomoses below the nail—glomus bodies, which are concerned with heat regulation.
Glomus bodies are important in maintaining acral circulation under cold conditions—
arterioles constrict with cold, but glomus bodies dilate. The nail beds of fingers and toes
contain such bodies (93–501 per cm2). Each glomus is an encapsulated oval organ 300
µm long, made up of a tortuous vessel uniting an artery and venule, a nerve supply and a
capsule; also within the capsules are many cholinergic muscle cells.

Figure 1.2

Digital blood and nerve supply: (a) showing arterial anastomoses; (b)
arterial supply from hand to digits (radio-opaque dye seen in arterises);
(c) major digital arteries and nerve supply.