Spinal Cord Venous Drainage

Study Notes

6 longitudinal interconnecting veins in the spinal cord, including: • Anterior spinal vein: runs in the midline • Posterior spinal vein: runs in the midline • Anterolateral spinal veins (2) • Posterolateral spinal veins (2)
Anterolateral and posterolateral veins are situated near the lines of attachment of ventral and dorsal nerve roots

2 main enlargements: • Cervical enlargement: consists of cord segments C3-T1 and provides innervation for the upper limb via the brachial plexus (C5-T1) • Lumbar enlargement: made up of segments L1-S3 and associated with innervation of the lower limb via the lumbar plexus (L1-L4) and sacral plexus (L4-S2)

Conus medullaris: conical termination of the spinal cord
Filum terminale: strand of connective tissue from the tip of the conus medullaris, extending caudally and attaching to the dorsal surface of the 1st coccygeal vertebra

31 bilaterally paired spinal nerves: • 8 cervical • 12 thoracic • 5 lumbar • 5 sacral • 1 coccygeal
Spinal nerves attach to the spinal cord as dorsal and ventral roots
Dorsal roots carry afferent fibers
Ventral roots carry efferent fibers
Cauda equina: lumbar and sacral roots descending below the termination of the cord in a leash-like arrangement

Translucent membrane investing the cord like a loose-fitting bag
Subarachnoid space: lies between the pia and arachnoid mater, containing cerebrospinal fluid (CSF)

Tough, fibrous membrane enveloping the cord loosely
Separated from the arachnoid by the subdural space
Separated from the bony wall of the vertebral canal by the epidural space
Notes: • Although the spinal cord terminates at vertebral level L1-2, the arachnoid and dural sheaths continue caudally to S2 • Spinal nerve roots pass towards their intervertebral foramina, evaginating the arachnoid and dura to form meningeal root sleeves • Arachnoid and dura become continuous with epineurium ensheathing the spinal nerve

Incompletely divided into 2 symmetrical halves by the dorsal median sulcus and ventral median fissure
Central canal: small canal in the center of the cord, continuous rostrally with the cerebral ventricular system
Grey matter: • Surrounds the central canal • Consists of nerve cell bodies, dendrites, and synaptic contacts • Dorsal horn: main site of primary afferent fibers, including substantia gelatinosa (important for transmission of nociceptive impulses to the brain) • Lateral horn: contains preganglionic sympathetic neurons • Ventral horn: contains alpha and gamma motor neurons (lower motor neurons)
White matter: contains ascending and descending nerve fibers

Arterial supply: • 3 longitudinal vessels run the length of the spinal cord: • Anterior spinal artery: arises from 2 vertebral arteries, descends along the ventral surface of the cord in the midline • Posterior spinal arteries: arise from vertebral arteries or posterior inferior cerebellar arteries, run on the posterolateral surface of the cord • Radicular arteries: derived from segmental vessels, pass through intervertebral foramina and divide into anterior and posterior branches