Overview of the Spinal Cord Segments and Nerve Roots

M.8, W. 1

How many cervical vertebrae are there?

7

How many thoracic vertebrae are there?

12

How many lumbar vertebrae are there?

5 (L1-L5)

How many sacral vertebrae are there?

Varied between species

What is a spinal cord segment?

portion of spinal cord that gives rise to one pair of spinal nerve roots

How many spinal cord segments do dogs and cats have?

35-38

Directionally, where do the spinal nerves leave the vertebral column? (Except C1-8)

Caudal to vertebrate of same number

What is the hotel that the vertebral nerves leave through called?

Intervertebral foramen

What is the end of the spinal cord called?

Cauda equina

What makes up the caudal equina?

Conus medullaris, filum terminale, lumbar/sacral/caudal nerve roots

What are intumescences?

Thickenings of the spinal column due to increased white matter

What are the three meninges?

Dura mater, arachnoid mater, pia mater

Which is the strongest of the meninges?

Dura mater

Where is the CSF found?

subarachnoid space

Which of the meninges surrounds the spinal cord/roots?

Pia mater

What is the structure called that attaches the pia mater to the arachnoid/dura?

Denticulate ligament

What type of nerve originates at the dorsal root?

Afferent

What type of nerve originates at the ventral root?

Efferent

What do the roots of nerves divide into at the spinal cord?

Rootlets

What does the dura mater become at the level of spinal nerves?

Epineurum

How can the dorsal root be distinguished from the ventral root?

Spinal ganglion

What are the supporting cells of the CNS?

Astrocytes, oligondendrocytes, microglial cells

Where is the grey matter found in the spinal cord?

Inside

Where is the white matter found in the spinal cord?

Outside

What lines the central canal of the spinal cord?

ependymal cells

How is the white matter of the spinal cord organized?

Dorsal funiculus, lateral funiculus, ventral funiculus

What are the ascending sensory tracts in the dorsal funiculus for?

Proprioceptive, tactile and nociceptive sensation

What are the ascending sensory tracts in the lateral funiculus for?

Proprioceptive, tactile, nociceptive, and thermal sensation

What are the descending sensory tracts in the lateral funiculus for?

Facilitating flexor muscle activity

What are the descending sensory tracts in the ventral funiculus for?

Facilitating extensor muscle activity

What are the major spinal nerves that make up the brachial plexus?

Suprascapular

Sububscapilar

Masculocutaneous

Axillary

Radial

Median

Ulnar

Where does the suprascapular nerve originate?

C5, 6, 7

Where does the subscapular nerve originate?

C6, 7

Where does the musculocutaneous nerve originate?

C6, 7, 8

Where does the axillary nerve originate?

C5, 8, 7

Where does the radial nerve originate?

C7, 8, T1, 2

Where does the median nerve originate?

C8, T1, 2

Where does the ulnar nerve originate?

C8, T1, 2

What are the major spinal nerves of the lumbosacral plexus?

Femoral

Obturator

Gluteal

Sciatic

Peroneal

Tibial

Pudendal

Where does the femoral nerve originate?

L4, 5, 6

Where does the obturator nerve originate?

L4, 5, 6

Where does the gluteal nerve originate?

L6, 7, S1, 2

Where does the sciatic nerve originate?

L6, 7, S1, 2

Where does the peroneal/tibial nerve originate?

Branch of sciatic

What functional testing can be done for the brachial plexus?

Flex (withdrawal) reflex

What functional testing can be done for the lumbosacral plexus?

Flexor withdrawal reflex, patellar reflex, perineal reflex