Presentation on theme: "Academic Half Day Dec 2008 Haythum O. Tayeb Chapter 9: The Spinal Cord."— Presentation transcript:
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)
Last points Somites: Vertebrae (sclerotomes) Dermatomes (skin and dermis) Myotomes (muscles) Relation of the spinal cord to the vertebral column By end of 1 st 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
Blood Supply of the Spinal Cord
Functional consideration of pathways
ModalityReceptorsFiber types Exteroceptive (GSA) Pain and temperature Bare nerve endings A δ (thin myelinated) C (non myelinated) Superficial touch Meissner’s Corpuscles Merkel’s receptors Aβ (Medium, myelinated) Proprioceptive (GSA) Proprio- ception Muscle Spindle Golgi Tendon Organ A α (large melinated) Aβ (medium myelinated) Deep touch, Pressure, Vibration Pacinian corpuscles Ruffini ending AβAβ Interoceptive (GVA) Viscero- sensory 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 Clark’s (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
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 Knowledge of the various pathways of the spinal cord is both fun and important in localization in clinical neurology.