1. Spinal Cord and Spinal Nerves

2. Spinal Cord Runs through the vertebral canal
Extends from foramen magnum to second lumbar vertebra
Regions
Cervical
Thoracic
Lumbar
Sacral
Coccygeal
Gives rise to 31 pairs of spinal nerves
All are mixed nerves
Not uniform in diameter
Cervical enlargement: supplies upper limbs
Lumbar enlargement: supplies lower limbs
Spinal Cord

3. Meninges of Spinal Cord
Connective tissue membranes
Dura mater: outermost layer; continuous with epineurium of the spinal nerves
Arachnoid mater: thin and wispy
Pia mater: bound tightly to surface
Forms the filum terminale
anchors spinal cord to coccyx
Forms the denticulate ligaments that attach the spinal cord to the dura
Spaces
Epidural: external to the dura
Anesthestics injected here
Fat-fill
Subdural space: serous fluid
Subarachnoid: between pia and arachnoid
Filled with CSF

4. Cross Section of Spinal Cord
Anterior median fissure and posterior median sulcus
deep clefts partially separating left and right halves
Gray matter: neuron cell bodies, dendrites, axons
Divided into horns
Posterior (dorsal) horn
Anterior (ventral) horn
Lateral horn
White matter
Myelinated axons
Divided into three columns (funiculi)
Ventral
Dorsal
lateral
Each of these divided into sensory or motor tracts
Cross Section of Spinal Cord

5. Cross Section of Spinal Cord
Commissures: connections between left and right halves
Gray with central canal in the center
White
Roots
Spinal nerves arise as rootlets then combine to form dorsal and ventral roots
Dorsal and ventral roots merge laterally and form the spinal nerve

6. Organization of Spinal Cord Gray Matter
Recall, it is divided into horns
Dorsal, lateral (only in thoracic region), and ventral
Dorsal half – sensory roots and ganglia
Ventral half – motor roots
Based on the type of neurons/cell bodies located in each horn, it is specialized further into 4 regions
Somatic sensory (SS) - axons of somatic sensory neurons
Visceral sensory (VS) - neurons of visceral sensory neur.
Visceral motor (VM) - cell bodies of visceral motor neurons
Somatic motor (SM) - cell bodies of somatic motor neurons

7. Gray Matter: Organization

8. White Matter in the Spinal Cord
Divided into three funiculi (columns) – posterior, lateral, and anterior
Columns contain 3 different types of fibers (Ascend., Descend., Trans.)
Fibers run in three directions
Ascending fibers - compose the sensory tracts
Descending fibers - compose the motor tracts
Commissural (transverse) fibers - connect opposite sides of cord

9. White Matter Fiber Tract Generalizations
Most consist of a chain of two or three neurons
All pathways are paired
one on each side of the spinal cord

10. White Matter: Pathway Generalizations