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
