Spinal Cord and Nerve Plexuses

spinal meninges

provide protection, physical stability, shock absorption; cover spinal cord and spinal nerve roots

dura mater

outermost/superficial layer, tough + fibrous, floating around spinal cord

arachnoid mater

thin, middle layer

subarachnoid space

found between arachnoid and pia mater, cerebrospinal fluid located here

pia mater

innermost layer, firmly bound to neural tissue, blood vessels supplying spinal cord are in this layer

spinal cord

ends around L1-L2, central canal is filled with CSF

conus medullaris

tapered conical termination of cord

filum terminale

fiber consisting of pia mater extending from conus to coccyx; prevents superior movement of spinal cord (anchors to coccyx)

spinal cord enlargements

areas concerned with sensory and motor innervation of limbs; cervical and lumbar

cervical enlargements

C4-T1; nerves to pectoral girdle and upper limbs

lumbar enlargements

T11-S1; nerves to pelvis and lower limbs

gray matter

butterfly or H shape in center of cord; cell bodies of neurons and glial cells, may vary in size

white matter

surrounds gray matter; contains myelinated and unmyelinated axons, organized into columns

ascending tract (within white matter column)

sensory info towards brain

descending tract (within white matter column)

motor info through spinal cord

nuclei

group of cell bodies in gray matter of spinal cord; sensory and motor

sensory nuclei

receive and relay info from peripheral receptors

motor nuclei

issue motor commands to peripheral effectors

somatic

control of skeletal muscle or sensory info from skeletal muscles, tendons, joints, and skin

visceral

digestion, circulation, or sensory info from visceral organs

dorsal horn

somatic and visceral sensory nuclei

lateral horn

visceral motor nuclei between T1-L2

ventral horn

somatic motor nuclei

cervical nerves (8)

C1-C8

thoracic nerves (12)

T1-T12

lumbar nerves (5)

L1-L5

sacral nerves (5)

S1-S5

coccygeal nerve (1)

Co1

dorsal ramus

sensory info from and motor info to skin and muscles in neck and back

ventral ramus

sensory and motor info for torso, internal organs, and limbs

nerve plexuses

composed of ventral rami of adjacent spinal nerves

cervical plexus

C1-C5 nerve root; phrenic nerve, C3, C4, C5 for diaphragm

brachial plexus

C5-T1 nerve root; innervate pectoral girdle and upper limb, root of neck towards axilla

lumbarsacral plexus

lumbar - T12-L4

sacral - L4-S4