2Y03 SPINAL CORD & SPINAL NERVE

lecture 18

spinal cord

communication link between brain and PNS, integrates information and produces responses, extends from the foramen magnum to L2 (like a super highway), NOT uniform in diameter

consus medullaris

the inferior end of the spinal cord

white matter in spinal cord

two halves; three columns in each half — each column divided into nerve tracts (fascicles), ascending and descending tracts myelinated axons

grat matter in spinal cord

composed of posterier, anterior, and lateral horns — ANS, sensory, and motor neurons

lateral horns function

connection to ANS

posterior horns function

where the axons of the sensory neurons enter the spinal cord, can either synapse here with interneurons or combine with a nerve tract in the white matter and then a ascend or descend in the spinal cord depending on the function of that particular sensory neuron

anterior horns functions

sometimes referred to as the motor horn, and its largest because it contains the cell bodies for the somatic motor neurons that go to skeletal muscle

gray and white commissures

axons that cross from one side of the spinal cord to the other

central canal

centre of the gray commissure, continuous with the ventricles

cervical enlargement

occurs between vertebrae C4 and T — associated with the extra nervous tissue that's needed to supply the additional structures of the upper

lumbosacral enlargement

occurs between the levels of T9 and T12 — associated with the extra nervous tissue that's needed to supply the additional structures of the lower limbs

filum terminale

an extension of the pia mater connective tissue covering around the spinal cord and it anchors the spinal cord to the inferior part of the vertebral column (coccyx) — It acts as a tether for the spinal cord to stop any movement in the superior direction

cauda equina

The hair-like nature of these nerves coming out of the bottom of the spinal cord

dura mater spinal cord

is the most superficial of the meningeal layers, made of dense, irregular connective tissue, thickest and strongest layers — separated from the bone by space

epidural space

space between the periosteum and the dura mater — filled with fat, blood vessels and areolar connective tissue → helps to protect the spinal cord as well as holding it in place

arachnoid mater spinal cord

a thin, avascular layer (no blood supply or blood vessels through layer), contains simple squamous epithelial cells and a delicate network of collagen and elastin fibers, fibers are arranged into a web-like pattern — similar to brain arrangement

subdural space spinal cord

a very small space and contains only a small amount of serous fluid

pia mater spinal cord

very important for maintaining the spinal cord within the vertebral canal: contains our blood vessels (supply the spinal cord) It tightly adheres to the spinal cord itself, has small extensions of itself that move towards the dura mater and connect it to the dura mater (occur at each exit route) — called denticulate ligaments

denticulate ligaments

extensions of the pia mater that move towards the dura mater, help anchor the spinal cord laterally to prevent side to side movement

CSF in spinal cord

cushions the spinal cord and allows for protection, and it also delivers nutrients and removes waste products

rootlets

found at each spinal level; either leave or enter the spinal cord; 6-8 total, are on both the dorsal and ventral surfaces of the spinal cord, pass through the subarachnoid space, pierce the arachnoid mater, merged together to form the spinal nerve. Each contains a ganglion

anterior or ventral root

where all the motor neurons are going to exit the spinal cord

posterior or dorsal root

contains all of the sensory neurons that are entering into the spinal cord; recognized by bulge in one of the roots off the spinal cord

spinal nerve

When the dorsal and ventral roots merged together

dorsal root ganglion

peripheral neurons are interacting with the spinal cord; sensory neurons will be in this bulge in the roots of the spinal nerve

polio

caused by a virus that attacks the cell bodies of the motor neurons that are in the anterior horn and some of the cranial nerve cell bodies, resulting in motor loss and eventually paralysis

Amyotrophic Lateral Sclerosis (ALS)

degeneration of the anterior horn of the spinal cord, as well as the motor axons descending the spinal cord; it also attacks the motor neuron cell bodies in the brain and the spinal cord resulting in loss of the ability to speak, swallow, and breath

somatic motor neurons

found in the anterior horn and exit via the ventral root

endoneurium

in the structure of a peripheral nerve, Immediately around the individual myelinated axons, it separates the axons from each other

fascicles

in the structure of a peripheral nerve, individual axons that are grouped together into bundles

perineurium

in the structure of a peripheral nerve, this connective tissue layer surrounds the individual axons that are grouped together into bundles (fascicles)

epineurium

the spinal nerve is surrounded by the most superficial of the connective tissue layer

posterior or dorsal ramus of spinal nerve

innervating the dorsal trunk muscles or the deep muscles of the back responsible for movements of the vertebral column, and also some of the skin and connective tissue on the back

anterior or ventral ramus of spinal nerve

thoraic region (T2-T12): form intercoastal nerves — remaining roots form the five plexuses

cervical plexus

roots: C1-C4

innervates superficial neck structures, skin of neck, posterior portion of head

contains → phrenic nerve

phrenic nerve

from C3-C5 (cervical and brachial plexuses); innervates diaphragm

brachial plexus

roots: C5-T1

3 trunks (upper middle lower), 6 divisions (anterior and posterior), 3 cords (posterior, lateral medial), 5 branches (axillary, radial, musculoctanenous, ulnar, median): supply to the shoulder and upper limbs

lumbar plexus

roots: L1-L4

two of the major nerves are obturator & femoral (supplies part of the lower limbs)

sacral plexus

roots: L4-S4

two major nerves are tibial & common fibular which are bound together to form the sciatic nerve (supply large portion to the lower limbs)

coccygeal plexus

roots: S5 to Co

muscles of pelvic floor, sensory information from skin over ______