Anatomy: Spinal Cord and nn

How many spinal nn are there

31 pairs (8 cervical, 12 thoracic, 5 lumbar, 5 sacral, and 1 fused coccygeal)

Epidural space

Area between bony and ligament outs walls of vertebral canal - where epidural anesthesia is administered during childbirth

What is the cauda equina?

'Horse's tail' - lumbar and sacral nn that have long dorsal and ventral roots and descend to reach their respective intervertebral foramina because the vertebral column grows more rapidly than the cord

GSA/somatosensory fibers

-Come from joints, skin, skeletal muscle into the CNS -cell bodies in the dorsal root ganglia -in cutaneous branches as postganglionic neurons of the sympathetic nn)

Dura mater

-Hard, tough outermost layer Closed sac from foramen magnum to S2 -surrounds nerve roots as they leave dural sac -becomes continuous with epineurum (outer CT sheath)

GVA/Viscerosensory fibers

-from viscera/vessels into the CNS -cell bodies in dorsal root ganglia -not in cutaneous nn

Epidural anesthesia

-larger space (epidural space) -catheter indwelling - additional injections -15-30min to kick in -can be given in cervical, thoracic, or lumbar level

GVE/Visceromotor fibers

-leave CNS and go to glands, smooth m, and cardiac m. (ANS) -2 neuron chain -preganglionic neuron cell body in lateral horn meets with postganglionic neuron -postganglioninc neuron in prevertebral or paravertebral ganglia goes to target organ

GSE/Somatomotor fibers

-leave CNS and innervate skeletal m. -cell bodies in the ventral horn -present in cutaneous n

General features of the spinal cord

-lies in vertebral canal -surrounded by coverings/meninges -length is from foramen magnum to L1 ish -continuous with brain -cervical and lumbar enlargements where more nn reside to supply the limbs

Spinal anesthesia

-smaller space (subarachnoid space) -usually 1 dose -5min onset -given below L2 to avoid spinal cord

Arachnoid mater

-spiders web -delicate membrane inside dura

Pia mater

-tender mother -thin, delicate membrane -intimately connected with surface of spinal cord and nerve roots -extends from conus medullaris to dural sac - 2 continuations: filum terminale and denticulate ligaments

Meninge definition

CT membrane that surrounds the spinal cord, nerve roots, and brain

What is the nervous system?

Central nervous system: brain and spinal cord Peripheral nervous system: 12 pairs of cranial nn, 31 pairs of spinal nn, and the autonomic ns

Denticulate ligaments

Continuation of pia mater that anchors spinal cord to dura mater so it is positioned laterally

Filum terminale

Continuation of pia mater that anchors the spinal cord. Spans from end of conus medullaris to coccyx

Ending of the spinal cord

Conus medullaris

3 meninges

Dura mater, arachnoid mater, and pia mater

Myotome

Group of mm supplied by single ventral root (motor) - more caudal supply distal mm and more rostral supply proximal mm

Gray matter of spinal cord

Nerve cell bodies in a butterfly shape containing a ventral horn, lateral horn (intermediate gray), and dorsal horn

Visceral fibers

Nerve fibers inner sting structures from smooth mm, cardiac m., and glands

Somatic fibers

Nerve fibers that Innervate skeletal mm, bones, joints, skin, and subcutaneous tissue

Peripheral nerve distribution

Nerves supplying the limbs are branches of plexuses and therefore contain nerve fibers from several spinal nn. Peripheral nerves are a bunch of nerves so damage depends on where the branches go to as well

Segmental nerve distribution

One nerve leaves the spinal cord and goes to a specific myotome, dermatome, or scleratome. It doesn't go to multiple places so any issues are more localized

Motor/efferent fiber direction

Out of the CNS

Dermatome

Patch of skin supplied by a single dorsal root and its ganglion (sensory) -trunk has identical dermatomes and peripheral n distributions -Limbs and have different

Nerve distribution in cervical, lumbar, and sacral region

Peripheral nerve distribution

Scleratome

Portion of bones and joints supplied by a single dorsal root and its ganglion (sensory)

Nerve distribution in the thoracic region

Segmental nerve distribution

Subarachnoid space

Space between arachnoid mater and pia mater where cerebrospinal fluid resides so spinal taps/lumbar punctures (detect hemorrhage or meningitis) and spinal anesthesia (L2-S2 - only filum terminale and cauda equina) occur here

Subdural space

Space between dura mater and arachnoid mater

How are the spinal nn organized with their associated vertebrae?

Spinal nerved C1-C7 are exit the vertebral column above their associated vertebrae. C8 exits below C7 and above T1 because there is no 8th cervical vertebrae. After this, each spinal n. Exits the vertebral column below their associated vertebrae.

Sensory/afferent fiber direction

To the CNS