Shelly Lwu Jan. 23, 2009 Spinal Cord

ž Extends from foramen magnum to L1 or L2 vertebra in an adult

ž Level / segments: — Cervical 8 — Thoracic 12 — Lumbar 5 — Sacral 5 — Coccygeal 1

— Each segment specified by the intervertebral foramina thru which the ant & post roots attached to that segment exit the vertebral canal Surface Features

ž Anterolateral sulcus ž Posterior median sulcus — Exit point for anterior roots ž Posterolateral sulcus — Not as distinct as — Entry point of dorsal roots posterolateral sulcus — Runs full length of cord ž Anterior median fissure ž Posterior intermediate sulcus — Prominent space dividing ant — Found in cervical & upper part of cord into halves thoracic regions — Contains delicate strands of — Gracile fasciculus – medial pia & sulcal branches of anterior spinal artery — Cuneate fasciculus – lateral Spinal Nerve

ž Dorsal root — Afferent fibers — Cell bodies in dorsal root ganglia

ž Ventral root — Efferent fibers — Cell bodies in ventral gray horns

ž Dorsal & ventral nerve roots unite at points of exit from vertebral canal to form spinal nerve Spinal Meninges and Spaces

ž Epidural space

ž Dura mater — Thecal sac at its caudal end (~S2 vertebra) is anchored to coccyx by filum terminale externum — Spinal cord attached to thecal sac by: ○ Dentate ligaments ○ Filum terminale internum – extends caudally from conus medullaris to caudal attenuated portion of the dural sac

ž Arachnoid mater — Adheres to inner surface of dura

ž Subarachnoid space — Continuous w/ subarachnoid space around brain & filled w/ CSF

ž Pia mater — Intimately attached to surface of cord Sections Through Spinal Cord

ž Levels assoc w/ limbs have greater amounts of gray matter

ž White matter increases from caudal to rostral — Level-by-level addition of ascending tracts & termination of descending tracts Regional Characteristics: Cervical

Cervical ž Prominent post & ant horns b/c of extensive sensory input & motor outflow to upper & lower extremities ž Obvious oval shape Regional Characteristics: Thoracic

Thoracic ž Large amount of white matter ž Both gracile & cuneate fasciculi present at upper thoracic levels (above T6); only gracile fasciculus present at lower thoracic levels (below T6) ž Posterior thoracic nucleus (dorsal nucleus of Clarke) – prominent cell group in medial parts of lamina VII, contains neurons of dorsal spinocerebellar tract ž Lateral horn formed by underlying intermediolateral cell column — T1~L2,3 – preganglionic sympathetic cell bodies Regional Characteristics: Lumbar

Lumbar ž Prominent post & ant horns ž Less white matter than at higher levels ž Cauda equina caudally Regional Characteristics: Sacral

Sacral ž Cord round & small ž Consists mainly of gray matter w/ white matter forming relatively thin shell ž Intermediate gray — S2~S4 – preganglionic parasympathetic cell bodies (less prominent) ž Substantia gelatinosa (lamina II) esp obvious White Matter

ž 3 regions composed of tracts or fasciculi — Dorsal funiculus: fasciculus cuneatus, fasciculus gracilis — Lateral funiculus: lateral corticospinal tract, spinothalamic tract — Ventral funiculus: reticulospinal tract, vestibulospinal tract, anterior corticospinal tract, medial longitudinal fasciculus Ascending Tracts Descending Tracts Somatotopic Organization of White Matter Tracts Gray Matter

ž Dorsal horn – laminae I to VI — Substantia gelatinosa (lamina I)

ž Ventral horn – laminae VIII & IX

ž Intermediate zone – lamina VII — Posterior thoracic nucleus (dorsal nucleus of Clarke) — Intermediolateral nucleus / cell column – T1 to L2

ž Composed of neuron cell bodies, dendrites, & initial part of axon, the axon terminals of fibers synapsing in this area, & glial cells ž Few myelinated fibers ž Based on shape, size, & distribution of neurons located in these areas, gray matter is divided into Rexed laminae I to IX, & area X around central canal Somatotopic Organization of the Ventral Horn Autonomic Nervous System Locations of neuronal cell bodies:

ž Sympathetic — Preganglionic – within intermediolateral cell column of T1~L2,3 — Postganglionic – within sympathetic chain or ganglia

ž Parasympathetic — Preganglionic – within brainstem nuclei (CNs III, VII, IX, & X) & intermediolateral cell column of S2~3 — Postganglionic – within intramural ganglion of the organ innervated Autonomic Nervous System

ž Paravertebral location of the sympathetic chain Arterial Supply

ž Anterior spinal artery — Supplies ant 2/3 ž Posterior spinal arteries x 2 — Supply post 1/3 Branches of vertebral arteries

ž Radicular arteries Branches from aorta

ž “Watershed zone” in midthoracic region Arterial Supply

ž Radicular arteries – dorsal & ventral arteries supply the dorsal & ventral roots of the spinal nerves & their coverings

ž Segmental medullary arteries – largely bypass roots to supplement blood supply to cord; occur irregularly in the place of radicular arteries — Artery of Adamkiewicz – usually between T9 & L2 on L side & arises from an inferior intercostal or upper lumbar artery

ž Arterial vasocorona – at each level, terminal branches of segmental medullary arteries join together to form an arterial network on surface of cord

ž Central branches of ASA – tend to alternate serving L & R sides of cord — 5 to 9 per segment of cord Arterial Supply

ž Posterior columns & peripheral parts of lateral & anterior funiculi supplied by PSA’s & arterial vasocorona

ž Most of gray matter & adjacent parts of white matter supplied by central branches of ASA Venous Drainage ž External & internal plexus of veins extend along length of vertebral column, forming a series of venous “rings” w/ extensive anastomoses around each vertebra

ž Venous plexuses drain through intervertebral veins into vertebral, posterior intercostal, subcostal, & lumbar & lateral sacral veins References

ž Felten DL & Jozefowicz RF. Netter’s Atlas of Human Neuroscience

ž Haines DE, ed. Fundamental Neuroscience for Basic and Clinical Applications, 3rd ed.

ž Moore KL & Dalley AF. Clinically Oriented Anatomy, 4th ed.

ž Snell RS. Clinical Neuroanatomy for Medical Students, 5th ed.