A morphometric study of intrafascicular vessels of mammalian sciatic nerve.

Intrafascicular vessel profiles were measured with a Quantimet image analyzer in 1-micron transverse sections of sciatic nerves of rats and compared with those of ("white") skeletal muscle. Blood vessels occupy the same percentage of the total tissue area in nerve and muscle tissues. The nerve, however, has much larger capillaries (about 1.7 X) spaced farther apart (about 2.5 X). Comparison of 3 1/2 month with 1-year-old rats showed that muscle capillaries increased in diameter (slightly, but significantly) at maturity, but those of the nerve decreased (also significantly). Vascular percentages of total tissue areas did not change. Nerve and muscle samples from monkey, rabbit, mouse, and cat show that the same striking pattern of large, widely spaced vessels distinguishes the nerve from other tissues. Minor interspecies variations exist. The nerve may contain as much blood as the muscle but its angioarchitecture suggests a lower exchange capacity.