Chapter 9: The Spinal Cord - McGill University

Chapter 9: The Spinal Cord - McGill University

Academic Half Day Dec 2008 Haythum O. Tayeb Chapter 9: The Spinal Cord Outline Review of: Highlights on embryology of the spinal cord

Structure of the spinal cord (anatomy) Regional charecteristics Blood supply Functional consideration of the pathways The spinal nerves (input and output) Grey matter columns White matter columns

Spinal Reflexes Embryology of the Spinal Cord The neural plate and caudal eminence

Day 18: Neural plate formation of neuro-ectoderm Caudal portion cervical, thoracic and lumbar cord. Day 20 (to 42): Appearance of caudal eminence Sacral and coccygeal levels Neural tube formation

Day 21: the edges of the neural plate (neural folds) enlarge posteromedially to meet at midline. Neural tube formation Neural fusion, starting at the adult cervical spinal cord.

Anterior neuropore closure: day 24. Posterior neuropore closure: day 26. Neural crests detach. Cells of the neural tube Ventricular zone ependyma of central

canal Subventricular zone macroglia Intermediate zone basal and alar plates (grey horns) Marginal zone axonal tracts (white

matter) Neural tube derivatives Basal plates venral horns. Alar plates dorsal horns. Interface intermediolateral column. Neural crest cells DRG.

Last points Somites: Vertebrae (sclerotomes) Dermatomes (skin and dermis) Myotomes (muscles) Relation of the spinal cord to the vertebral

column By end of 1st trimester: both formed and have equal length Both grow caudally but vertebral column faster Spinal cord seems drawn rostrally. Intervertebral foramina move caudally.

Hence the cauda equina, the lumbar cistern Structure of the Spinal Cord Regional Charecteristics Blood Supply of the Spinal Cord

Functional consideration of pathways Exteroceptiv e (GSA) Propriocepti

ve (GSA) Interoceptiv e (GVA) Modality

Receptors Fiber types Pain and temperatu re

Bare nerve endings A (thin myelinated) C (non myelinated) Superficial

touch Meissners Corpuscles Merkels receptors A (Medium, myelinated)

Proprioception Muscle Spindle Golgi Tendon Organ A (large melinated)

A (medium myelinated) Deep touch, Pressure, Vibration Pacinian

corpuscles Ruffini ending A Viscerosensory Visceral

receptors for nociceptive stimuli C Grey Matter Laminae

The white matter Tracts Ascending Descending Propriospinal White matter - Ascending tracts

Posterior column tracts The anterolateral system Spino- cerebellar tracts Posterior: from Clarks (dorsal) nucleus (lamina 6,7) Anterior: from spinal

border cells (lamina 5-8) Posterior column tracts (gracile and cuneate fasciculi) T6 The anterolateral system

Spinothalamic Spinomesencephalic (spinotectal, spinoperiaqueductal) Central pain modulation Spinoreticular fibers Arousal with pain

Spinohypothalamic Autonomic and limbic responses to pain The anterolateral system White matter Descending Tracts

Lateral Faniculus Lateral corticospinal tracts Rubrospinal Reticulospinal Fastigiospinal Raphespinal Hypothalamospinal Anterior Faniculus

Anterior corticospinal tract Vestibulospinal tracts Retiulospinal tracts Medial longitudinal fasciulus Lateral corticospinal tract Anterior corticospinal tracts

Rubrospinal tract Present in cervical levels Stimulates flexor tone and inhibits extensor tone Possible role in decorticate flexor posturing

Uncertain role in humans Reticulospinal and tectospinal tracts Reticulospinal: uncrossed Pontine (anterior faniculus) Medullary (lateral

faniculus) Extensor tracts Tectospinal: direction of head and eye movements Vestibulospinal tracts Vestibulospinal tracts

Lateral (uncrossed) Medial (bilateral) Extensor Spinal Reflexes Muscle Stretch Reflex

Flexor reflex Crossed extension reflex Quick clinical refresher - 2 slides Spinal cord syndromes

Spinal Cord Syndromes In conclusion The spinal cord develops from the caudal portion of the neural plate and the caudal eminence.

The structure of the spinal cord differs according to the level due to the varying degrees of grey and white matter The spinal cord constitutes the major conduit and a relay station from and to the brain, conveying afferent and efferent somatic and visceral information. The spinal cord also functions in spinal

reflexes Thanks for listening!! References Haines Blumenfeld

Snells neuroanatomy Grays anatomy

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