The Spinal Cord Blood Vessels

This chapter focuses on the blood vessels and blood flow in the spinal cord. Blood flow is intricately related to function in the spinal cord, as in the rest of the nervous system. Along with, exchange of gases and nutrients, the effects of circulatory convection are important for the optimal operation of nervous tissue. Metabolic heat in active brain areas need to be cleared by circulatory convection requiring enhancement of blood flow to avoid a local elevation in temperature. Local cooling by circulatory convection could result in enhanced synaptic efficacy. In addition, perfused blood vessels provide a “sink” for the effective dissipation by diffusion of neurotransmitter gradients, thus accelerating the termination of neurotransmitter action. The circulation also controls partial pressure of gases in the neuronal microenvironment. A capillary network can be found on the surface of the human spinal cord at the 8 mm stage and by the end of the fourth month of pregnancy, capillaries are evenly distributed between gray and white matter. Angiogenesis is central to the development and differentiation of the nervous system, and a concerted action of a number of angiogenic factors leads to the parallel growth and differentiation of nerve cells and the blood vessel networks. The arterial supply to the spinal cord originates from ventral, posterolateral and dorsal systems that extend throughout the entire cord. An intricate venous plexus is found on the surface of the spinal cord. On the ventral side, a ventral spinal vein (vsv) is found dorsal or adjacent to the ventral spinal artery. There is no evidence for lymph vessels inside the spinal cord or any part of the central nervous system. However, it has been known for over a century that large tracer molecules and particles added to the cerebrospinal fluid can be found in the lymphatics of the head, neck and spine at a later time.