Blood Supply of the Spinal Cord
The spinal rami of the sacral, lumbar, intercostal, or vertebral arteries, as the case may be, accompany the spinal nerves through the intervertebral foramina, traverse the dura mater and arachnoid, and each divides into a dorsal and a ventral radicular artery. These accompany the nerve-roots to the surface of the cord, and there break up into an anastomosing plexus in the pia mater. From this plexus are derived three tortuously coursing longitudinal arteries and numerous independent central branches, which latter penetrate the cord direct. Of the longitudinal arteries, the anterior spinal artery zigzags along the anterior median fissure and gives off the anterior central branches, which pass into the fissure and penetrate the cord. These branches give of a few twigs to the white substance in passing, but their most partial distribution is to the ventral portion of the grey substance. The two posterior spinal arteries, one on each side, course near the lines of entrance of the dorsal root-fibers. They each branch and anastomose, so that often two or more posterior arteries may appear in section upon either side of the dorsal root. These give off transverse or central twigs to the white substance, but especially to the grey substance of the dorsal horns. Of the remaining central branches many enter the cord along the efferent fibers of the ventral roots, and are distributed chiefly to the grey substance; others from the peripheral plexus throughout penetrate the cord and break up into capillaries within the white substance. Some of the terminal twigs of these also enter the grey substance. The blood supply of the grey substance is so much more abundant than that of the white substance that in. injected preparations the outline of the grey figure may be easily distinguished by its abundance of capillaries alone. The central branches are of the terminal variety. In the white substance the capillaries run for the most part longitudinally, or parallel with the axons.
The venous system is quite similar to the arterial. The blood of the central arteries is collected into corresponding central venous branches which converge into a superficial venous plexus in which are six main longitudinal channels, one along the posterior median sulcus, one along the anterior median fissure, and one along each of the four lines of the nerve-roots. These comprise the posterior and anterior external spinal veins.
The internal spinal veins course along the ventral surface of the grey commissure, and arise from the convergence of certain of the twigs of the anterior central vein. The posterior central vein courses along the posterior median septum in company with the posterior central artery, and empties into the median dorsal vein. The venous system communicates with the coarser extra-dural or internal vertebral plexus chiefly by way of the radicular veins.
From Morris's treatise on anatomy.