A&P spinal cord

number of pairs of spinal nerves

number of pairs of spinal nerves

31 total, 8 cervical, 12 thoracic, 5 lumbar, 5 sacral, 1 coccygeal

cervical enlargement

supplies nerves to the shoulders and upper limbs.

lumbar enlargement

supplies nerves to the pelvis and lower limbs.

conus medullaris

tapered, cone-shaped part of the spinal cord inferior to the lumbar enlargement

cauda equina

collection of dorsal and ventral roots of spinal segments L2 to S5 (name comes from resemblance of a horses tail).

falilum terminale

a thin cord that ties the lower end of the spinal cord to the coccyx

denticulate ligaments

extend from pia mater through arachnoid mater to dura mater.

white matter

contains large numbers of myelinated and unmyelinated axons, this area contains tracts.

gray matter

dominated by cell bodies of neurons, neuroglia, and unmyelinated axons, surrounds small central canal, forms a butterfly shape, three horns in each half of gray matter.

posterior median sulcus

shallow groove on the posterior surface

anterior median fissure

deep groove along anterior surface

ventral root

contains axons of motor neurons

dorsal root

contains axons of sensory neurons whose cell bodies are in the dorsal root ganglion

dorsal root ganglion

contains cell bodies of sensory neurons, each spinal cord segment has pair of dorsal root ganglia (one on each side)

spinal nerve

formed by union of two roots, contains axons of sensory and motor neurons, spinal nerve divides into ventral and dorsal rami

posterior gray horn

contains somatic and visceral sensory nuclei

lateral gray horn

found only in thoracic and lumbar segments, contains visceral motor nuclei

anterior gray horn

contains motor nuclei

length of spinal cord

about 45 cm (18 in)

lumbar puncture

procedure for withdrawing sample of cerbrospinal fluid, needle inserted into subarachnoid space in lower lumbar region inferior to tip of conus medullaris.

dorsal ramus

innervates muscles, joints, and skin of the back

ventral ramus

innervates structures in the upper and lower limbs and the lateral and anterior trunk

communicating rami

present in the throacic and superior lumbar segments of spinal cord, contain axons of sympathetic neurons

posterior white column

between posterior gray horns and posterior median sulcus

lateral white column

between the anterior and posterior columns

anterior white column

between the anterior gray horns

anterior white commissure

interconnects anterior white columns

bone

vertebrae for a canal for the spinal cord

epidural fats

between the bone and the dura mater

dura mater

outermost layer of the spinal meninge, covering of the spinal cord, tough and fibrous

arachnoid mater

middle middle layer of the spinal meninge, includes simple squamous epithelium, arachnoid membrane, located in the subarachnoid space

pia mater

innermost layer of the spinal meninge, meshwork of elastic and collagen fibers, firmly bound to underlying neural tissue

ascending tracts

carry sensory information

descending tracts

carry motor commands

dermatome

an area innervated by a single pair of nerves, boundaries of adjacent dermatomes overlap, clinically important to determine extent of damage or injection of spinal nerve or dorsal root ganglion.

nerve plexus

complex, interwoven network of nerves, formed during development, ventral rami of adjacent spinal nerves converge and blend their fibers producing plexuses.

cervical plexus

consists of ventral rami of spinal nerves C1-C5, branches innervate muscles of the neck, skin of the neck, skin of the superior part of the chest, and the diaphragm.

brachial plexus

innervates the pectoral girdle and upper limbs

lumbar and sacral plexuses

arise from the lumbar and sacral segments of spinal cord, innervate the pelvic girdle and lower limbs, contain the sciatic nerve.

innate reflex

result from connections formed during development, genetically or developmentally programmed, generally appear in predictable sequence from simplestto more complex.

acquired reflexes

conditioned reflexes, rapid and automated, learned, enhanced by repetition

babinski sign/reflex

stroking foot on the lateral side of the sole, positive response is extention of the lallux and fanning of other toes.