Topic 6.2 : Spinal Cord & Spinal Nerves

Primary anatomical and functional roles of the spinal cord

Connects brain with body and acts as a center for integrating reflexes

Number of cervical spinal cord segments and spinal nerve pairs

8 pairs (C1-C8)

Number of thoracic spinal cord segments and spinal nerve pairs

12 pairs (T1-T12)

Number of lumbar spinal cord segments and spinal nerve pairs

5 pairs (L1-L5)

Number of sacral spinal cord segments and spinal nerve pairs

5 pairs (S1-S5)

Number of coccygeal spinal cord segments and spinal nerve pairs

1 pair (Co1)

Total number of spinal nerve pairs in the human body

31 pairs

Functional role of spinal cord gray matter

Integration center and reflex processing

Functional role of spinal cord white matter

Conduction of nerve impulses

Ascending spinal cord pathways functional direction

Carries sensory information from receptors upward to the brain

Descending spinal cord pathways functional direction

Carries motor orders from brain downward to effectors

Clinical deficit resulting from a cervical spinal cord lesion

Tetraplegia and possible respiratory compromise

Clinical deficit resulting from a thoracic spinal cord lesion

Paraplegia and altered sensory and sympathetic function

Clinical deficit resulting from a lumbar spinal cord lesion

Weakness in lower extremities and decreased reflexes

Hallmark clinical triad of cauda equina syndrome

Saddle anesthesia, sphincter dysfunction, and variable lower limb weakness

Vertebral level of spinal cord termination in the adult

L1-L2 vertebral level

Embryological reason why the adult spinal cord ends at L1-L2

Spinal cord segments are shorter than corresponding vertebral segments

Tapered conical inferior termination of the spinal cord

Conus medullaris

Collection of nerve roots descending below the conus medullaris

Cauda equina

Nerve root types composing the cauda equina

Lumbar, sacral, and coccygeal roots

Central fibrous filament anchoring the conus medullaris to the coccyx

Filum terminale

Specific meningeal layer forming the filum terminale internum

Pia mater

Superior anatomical boundary of the spinal cord

Bulbomedullary junction at the foramen magnum

Two regional physiological enlargements of the spinal cord

Cervical enlargement and lumbar enlargement

Primary neuronal cell bodies located within the anterior horns

Somatic motor neurons

Route taken by anterior horn somatic motor axons leaving the cord

Ventral root of the spinal nerve

Primary neuronal cell bodies located within the posterior horns

Sensory neurons involved in conscious sensation

Route taken by incoming sensory axons reaching the posterior horn

Dorsal root of the spinal nerve

Ascending route taken by conscious sensory axons from posterior horn cells

Posterior funiculi toward the brainstem

Neuronal cell bodies located within the lateral horns

Interneurons for reflex arcs and autonomic nervous system neurons

Primary information modality conducted by anterior funiculi

Conscious motor information

Primary information modality conducted by posterior funiculi

Conscious sensory information

Primary information modality conducted by lateral funiculi

Unconscious sensory and motor information

Anatomical naming rule for central nervous system tracts

Begins with origin site and ends with termination and synapse site

Functional trajectory of ascending or afferent spinal tracts

Carries sensory information from receptors to sensory cerebral cortex

Functional trajectory of descending or efferent spinal tracts

Carries motor orders from cerebral cortex to effector muscles

Anatomical structures uniting to form a mixed spinal nerve

Sensory dorsal root and motor ventral root

Bony openings through which spinal nerves exit the vertebral column

Intervertebral foramina

Emergence site of the first cervical spinal nerve (C1)

Between the occipital bone and the first cervical vertebra (atlas)

Spinal cord segment anatomical definition

Portion of the spinal cord situated between two adjacent spinal nerves

Muscular distribution of spinal nerve ventral rami

Muscles of the anterolateral surfaces of trunk and limbs

Ventral rami plexus formation anatomical rule

Forms plexuses in the limbs but does not form plexuses in the trunk

Muscular distribution of spinal nerve dorsal rami

Exclusively supplies muscles of dorsal embryological origin

Target back muscles innervated exclusively by dorsal rami

Multifidus, rotatores, and longissimus

Trajectory and targets of the recurrent meningeal branch

Re-enters intervertebral foramen to innervate blood vessels and meninges

Spinal nerve branches connecting directly with autonomic nervous system

White and gray rami communicantes