Back 2

Front 1

Vertebral Canal

Back 1

The vertebral foramen is enclosed by the pedicles, the lamina and the body. Stacking vertebra connects the foramen into the vertebral canal.

The canal houses and protects the spinal cord and meninges (spinal membranes).

Front 2

Spinal Cord Length and Characteristics

Back 2

Spinal Cord has 31 pairs of spinal nerves.

Extends from the medulla oblongata (brainstem).

Extends from base of skull to ~L2 vertebrae level (sometimes L1 or T12).

Only occupies superior 2/3rds of canal.

Front 3

Spinal Cord Growth

Back 3

In embryo, occupies entire length of column. Spinal nerves pass through IV foramen at their level of origin.

During devo, column grows faster than cord, so nerves must course obliquely through canal and exit at their appropriate levels.

Because of this, sacral and coccygeal nerves must grow the longest. The collection of nerve roots past the end of the cord is the cauda equina.

Front 4

Dural Sac

Back 4

Tough protective coat made by the dura mater. Goes from base of skull to S2.

Front 5

Conus Medullaris

Back 5

Tapered cone shaped end of spinal cord. Around L1/L2. Extending form the cone is the filum terminale. Remnant of the caudal spinal cord that goes all the way down, anchors.

Internal filum goes to end of dural sac, external filum goes to coccyx.

Front 6

Spincal Cord Enlargements

Back 6

Two of them:

1) Cervical enlargement innervates upper limbs
2) Lumbosacral enlargement innervates lower limbs.

Front 7

Difference in spinal cord and spinal column levels

Back 7

Because of short cord, L5 cord level for example is level with T12 column level. Its nerve, L5 nerve, exits at L5 column level though.

Since there are 8 cervical nerves but only 7 cervical vertebrae, C1-C7 exit above their associated vertebrae. C8-S5 exit the column below their associated vertebra.

Front 8

Spinal Meninges

Back 8

1) Dura Mater
2) Arachnoid Mater
3) Pia Mater

Along with cerebrospinal fluid (CSF), help support/protect spinal cord.

Front 9

Dura Mater

Back 9

Outer most meninges. Tough fibro-elastic tissue. Extends laterally into IV foramen. Makes dural sleeve, which fuses with outer covering of spinal nerve.

Small nerves that arise from spinal nerve are recurrent meningeal nerves. Convey information (sensory) from dura mater.

Front 10

Arachnoid Mater

Back 10

Intermediate meninge. Delicate fibrous membrane lining the inside of the dura. Encloses the CSF which fills the subarachnoid space (SAS). The latter contains spinal cord, spinal nerve roots, dorsal root ganglion.

Arachnoid is pushed against dura by CSF pressure. The SAS is continuous with the SAS around the brain!!

Front 11

Pia Mater

Back 11

Innermost of the meninges. Firmly adheres to the surface of the cord. Denticulate ligaments are lateral extensions of the pia between dorsal and ventral roots. Anchor the cord laterally.

Front 12

Epidural Space

Back 12

Between vertebral canal and dura mater. Contains fat and internal venus plexus. The latter drains blood from veins of cord/body via the basivertebral vein. Neither the plexus nor the basilateral have valves, so blood can flow up and down the column.

Front 13

Lumbar Spinal Tap

Back 13

Used to obtain sample of CSF. Lower lumbar region is ideal (L3-L5).
Patients lie down with column flexed to spread lamina/spinous processes.

Insert needle through ligamentum flavum/dura arachnoid membranes.

Front 14

Caudal Epidural Block

Back 14

Formerly common anesthetic procedure. Inject anesthetic into epidural space in sacral canal. Bathe nerves that convey pain from lower birth canal/pelvic floor.

Front 15

Arteries of the Spinal Cord

Back 15

Supply comes from the vertebral artery, the intercostal arteries and more.

These give off branches that perfuse the cord. The branches provide longitudinal vessels. Feeder or helper vessels then go off to the sides.

The longitudinal vessels are made of 1 anterior spinal artery (from vertebral artery) and 2 posterior spinal arteries (from vertebral artery too).

Intercostal arteries form the aorta give rise to spinal arteries that enter EVERY IV foramen.
These spinal arteries then follow and perfuse the dorsal/ventral roots.

Some spinal arteries are huge, and are called segmental medullary arteries. They reinforce the anterior/posterior longitudinal arteries. Biggest one is great anterior segmental artery. (aka Adamkiewicz artery). Reinforces circulation of lower 2/3 of cord.

Front 16

Posterior Longitudinal Ligament

Back 16

Inside canal. Blends with anulus fibrosus of the IV disks. The ligament is somewhat deficient laterally. The fusion helps prevent disk slippage.

Front 17

Herniated Disc

Back 17

Anulus weakens with age/trauma. If it tears, the nucleus pulposus can herniate. This usually happens posterolaterally.

The hernia can impinge on cauda equina/cord or spinal nerves.

This is common clinical condition. 95% happen around L4/L5 (affects L5 nerve) or L5/S1 level (affects S1 nerve).

Front 18

Dermatomes

Back 18

Area of skin innervated by single spinal nerve or spinal cord level. Sensory information from toe, for example, returns to cord via S1 spinal nerve, enters at S1 cord level (=L1 vertebral level). The sensory info enters via DRG. Cell bodies are in the DRG, so damage to a DRG or single spinal nerve can cause loss of feeling of a given dermatome.

Front 19

Shingles

Back 19

Herpes zoster is chicken pox virus in kids. In some, it remains dormant in DRG cells. If it becomes active, a rash erupts (shingles) along given dermatome. Can be very painful.

Front 20

Specific Dermatomes

Back 20

C5 --> tip of shoulder
C6 --> Thumb
C7 --> Index fingert
C8 --> Little finger
T1--> Medial arm