Lecture 17 - Spinal Cord

Question 1

What are the divisions of the somite and what is derived from each division?

L17 S7

Answer 1

Dermatome
-dermis

Myotome
-muscle

Sclerotome
-skeleton

Question 2

What is a dermatome?
What is a myotome?

L17 S11

Answer 2

Dermatome:
-area of skin supplied with afferent nerve fibers by a single posterior spinal root

Myotome:

• all muscles innervated by a single efferent anterior root
• most muscles innervated by more than one myotome

Question 3

What are the gross anatomical features of the spinal cord?

L17 S18-19

Answer 3

Enlargements:

• cervical (C3-T1)
• lumbar (L1-S2)

Conus medullaris:
-termination of spiral cord at L2

Cauda equina

Film terminals (meningeal filament extending from census medullaris)

Spinal nerves:

• 8 cervical
• 12 thoracic
• 5 lumbar
• 5 sacral
• 1 coccygeal

Plexuses:

• cervical (C1-4)
• brachial (C5-T1)
• lumbrosacral (L1-S4)

Question 4

Describe the cross-sectional anatomy of the spinal cord.

L17 S24-25

Answer 4

Gray matter (horns):

• posterior horn: incoming sensory information
• anterior horn: cell bodies of alpha motor neurons
• lateral horns: cell bodies of autonomic neurons (located in thoracic and lumbar region)

White matter (columns/funiculi):

• myelinated tracts
• posterior columns
• anterior columns
• lateral columns

Commissures:

• white (anterior and posterior)
• gray (anterior and posterior)

Question 5

Describe the anatomy of spinal nerves.

L17 S27-28

Answer 5

Dorsal rootlets:

• forms dorsal root and root ganglion
• carries afferent fibers

Ventral rootlets:

• forms ventral root
• carries efferent neurons

Spinal nerve:

• formed by dorsal and ventral roots
• mixture of afferent and efferent neurons

Primary rami:

• dorsal rami: to deep back muscles (epaxial) and skin of back
• ventral: to non-deep back muscles (hypaxial) and rest of skin

Autonomic rami:

• white ramus communicans: preganglionic sympathetic fibers from lateral horns
• grey ramus communicans: postganglionic sympathetic fibers back to spinal nerve

Question 6

What is the anatomy of the meningeal covering and its associated spaces? (from superficial to deep)

L17 S33-34

Answer 6

• epidural space (only present in the spine)
• dura mater
• subdural space
• arachnoid mater
• subarachnoid space (contains CSF)
• pia mater
• denticulate ligaments