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20 Cards in this Set

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Vertebral Canal
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).
Spinal Cord Length and Characteristics
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.
Spinal Cord Growth
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.
Dural Sac
Tough protective coat made by the dura mater. Goes from base of skull to S2.
Conus Medullaris
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.
Spincal Cord Enlargements
Two of them:

1) Cervical enlargement innervates upper limbs
2) Lumbosacral enlargement innervates lower limbs.
Difference in spinal cord and spinal column levels
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.
Spinal Meninges
1) Dura Mater
2) Arachnoid Mater
3) Pia Mater

Along with cerebrospinal fluid (CSF), help support/protect spinal cord.
Dura Mater
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.
Arachnoid Mater
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!!
Pia Mater
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.
Epidural Space
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.
Lumbar Spinal Tap
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.
Caudal Epidural Block
Formerly common anesthetic procedure. Inject anesthetic into epidural space in sacral canal. Bathe nerves that convey pain from lower birth canal/pelvic floor.
Arteries of the Spinal Cord
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.
Posterior Longitudinal Ligament
Inside canal. Blends with anulus fibrosus of the IV disks. The ligament is somewhat deficient laterally. The fusion helps prevent disk slippage.
Herniated Disc
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).
Dermatomes
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.
Shingles
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.
Specific Dermatomes
C5 --> tip of shoulder
C6 --> Thumb
C7 --> Index fingert
C8 --> Little finger
T1--> Medial arm