Vascular Supply Of The Spinal Cord

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A. Anterior spinal artery. There is only one anterior spinal artery, which arises from the vertebral arteries. It supplies the ventral two-thirds of the spinal cord.

B. Posterior spinal arteries. There are two posterior spinal arteries that arise from the vertebral arteries or the posterior inferior cerebellar arteries. They supply the dorsal one-third of the spinal cord.

C. Radicular arteries. The radicular arteries arise from the vertebral, deep cervical, ascending cervical, posterior intercostal, lumbar, and lateral sacral arteries. They enter the vertebral canal through the intervertebral foramina and branch into the anterior and posterior radicular arteries.

D. Great radicular artery (artery of Adamkiewicz)

1. The great radicular artery usually arises on the left side, from a posterior intercostal artery or a lumbar artery.

2. This artery is clinically important because it makes a major contribution to the anterior spinal artery. It also provides the main blood supply to the lower part of the spinal cord.

3. Ligation of the great radicular artery during resection of an abdominal aortic aneurysm may result in anterior spinal artery syndrome. Clinical findings include: paraplegia, impotence, loss of voluntary control of the bladder and bowel (incontinence), and loss of pain and temperature sensation (although vibration and proprioception sensation are retained).

III. THE SPINAL NERVE (Figures 2-1A and 2-2). There are 31 pairs of spinal nerves: 8

cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 coccygeal. Each spinal nerve has several components, as indicated below.

A. Small bundles of nerve fibers called root filaments, or rootlets (see Figure 2-1), arise from the dorsal and ventral surfaces of the spinal cord.

Figure 2-2. Components of a typical thoracic spinal nerve. The four functional components are the general somatic afferent (GSA), general somatic efferent (GSE), general visceral afferent (GVA), and general visceral efferent (GVE). The muscle stretch (myotactic) reflex includes the neuromuscular spindle, GSA dorsal root ganglion cell, GSE ventral horn motor neuron, and neuromuscular junction. DRG = dorsal root ganglion; DPR = dorsal primary ramus; GR = gray communicating ramus; PARA = paravertebral (sympathetic chain) ganglion; PRE = prevertebral ganglion; SN = splanchnic nerve; VPR = ventral primary ramus; WR = white communicating ramus.

Spinal Cord White Ramus

Figure 2-2. Components of a typical thoracic spinal nerve. The four functional components are the general somatic afferent (GSA), general somatic efferent (GSE), general visceral afferent (GVA), and general visceral efferent (GVE). The muscle stretch (myotactic) reflex includes the neuromuscular spindle, GSA dorsal root ganglion cell, GSE ventral horn motor neuron, and neuromuscular junction. DRG = dorsal root ganglion; DPR = dorsal primary ramus; GR = gray communicating ramus; PARA = paravertebral (sympathetic chain) ganglion; PRE = prevertebral ganglion; SN = splanchnic nerve; VPR = ventral primary ramus; WR = white communicating ramus.

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