Anatomy Lecture 3: Spinal Cord

Question 0

Structures of the central nervous system

Answer 0

Brain and spinal cord

Question 1

What are the major subdivisions of the nervous system?

Answer 1

Central nervous system (CNS)

Peripheral nervous system (PNS)

Question 2

Structures of the peripheral nervous system

Answer 2

All parts external to the CNS:
12 pairs of cranial nerves,
31 Paris of spinal nerves,
Peripheral portions of autonomic nervous system (ANS)

Question 3

What are the functional divisions of year nervous system and their definitions?

Answer 3

1. Somatic: innervates structures in body wall (skeletal m., skin, bones)
2. Autonomic: innervates viscera (smooth m., cardiac m., glands)

Question 4

What are 4 characteristics of the spinal cord?

Answer 4

1. Solid structure with hollow central canal containing cerebrospinal fluid (CNF)
2. Two types of tissue: grey and white matter
3. Diameter varies along length of cord
4. Has 31 segments, 1 segment per pair of spinal nerves

Question 5

What are characteristics of spinal cord grey matter?

Answer 5

1. Includes neuron cell bodies
2. Centrally situated in spinal cord
3. Cross-section shaped like H (or butterfly), with 2 dorsal horns and 2 ventral horns

Question 6

What are characteristics of spinal cord white matter?

Answer 6

1. Consists if axons and glial cells, no neuron cell bodies

2. Surrounds grey matter

Question 7

What are the spinal enlargements called and what do honey relate to?

Answer 7

1. Cervical enlargement - relates to upper limbs

2. Lumbar enlargement - relates to lower limbs

Question 8

Define conus medullaris

Answer 8

Tapered inferior end of spinal cord below lumbar enlargement.

Question 9

What are the spinal cord segments and how many segments correspond to them?

Answer 9

1. Cervical segments: 8
2. Thoracic segments: 12
3. Lumbar segments: 5
4. Sacral segments: 5
5. Coccygeal segments: 1

Question 10

What are the constituents of each spinal nerve?

Answer 10

1. Rootlets emerge from spinal cord and unite to form dorsal and ventral roots
2. Spinal nerve proper (mixed spinal nerve) formed from Union of dorsal and ventral roots
3. Spinal nerve proper divides to form dorsal and ventral rami
4. Recurrent meningeal (sinuvertebral) nerve

Question 11

What are characteristics of the dorsal (posterior) root?

Answer 11

1. Carries sensory (afferent) fibers toward spinal cord

2. Dorsal root ganglion: swelling at distal end of root, contains sensory fiber cell bodies

Question 12

Where are dorsal root ganglion found throughout the segments of the spine?

Answer 12

1. Cervical: ganglia extend lateral to intervertebral foramina
2. Thoracic/Lumbar: ganglia within foramina, but usually don’t extend beyond
3. Sacral: ganglia with in sacral canal medial to intervertebral foramina

Question 13

Usually the first cervical nerve has no dorsal root, which nerve takes over?

Answer 13

C2

Question 14

What are the characteristics of the ventral root?

Answer 14

1. Carries motor (efferent) fibers away from the spinal cord
2. Cell bodies of these motor fibers are in spinal cord grey matter
3. Two types: somatic and visceral (autonomic) motor fibers

Question 15

What are somatic motor fibers and where are they found?

Answer 15

Control voluntary (skeletal, striated) muscle fibers. Present in every ventral root.

Question 16

What are visceral (autonomic) motor fibers, what are the different types, and where are they found?

Answer 16

Control involuntary muscle fibers and certain glands.
Two types: sympathetic and parasympathetic, both preganglionic
Sympathetic motor fibers carried in T1-L2 ventral roots only
Parasympathetic motor fibers carried in S2-S4 ventral roots only

Question 17

What types of fibers do spinal nerve proper (mixed spinal nerve) carry?

Answer 17

Carry somatic motor, sympathetic, and sensory fibers irrespective of spinal cord level.

Question 18

What are the characteristics of the dorsal ramus?

Answer 18

1. Supplies both motor and sensory innervation to deep back muscles
2. Gives off posterior cutaneous nerve to skin of back

Question 19

What are the characteristics of the ventral ramus?

Answer 19

1. Supplies both motor and sensory innervation to muscles of lateral and anterior body wall, and limbs
2. Has branches to skin: Lateral and Anterior cutaneous nerve
3. Ventral rami that supply limbs and neck for a plexus

Question 20

In the sacral region, where do the rami exit through?

Answer 20

Dorsal rami emerge through dorsal sacral foramina and ventral rami emerge through ventral sacral foramina.

Question 21

Which rami has a larger diameter?

Answer 21

The ventral ramus has a larger diameter except the 1st and 2nd cervical spinal nerves.

Question 22

What is the C2 dorsal ramus called?

Answer 22

The greater occipital nerve.

Question 23

What connects the sympathetic trunk to the ventral rami?

Answer 23

Rami communicantes

Question 24

What is the recurrent meningeal (sinuvertebral) nerve?

Answer 24

Arises directly from the spinal nerve proper or from the ventral ramus and returns through the intervertebral foramen to provide innervation to dura mater, epidural fat, blood vessels, etc.

Question 25

Where does the adult spinal cord end?

Answer 25

L1-L2 intervertebral disc

Question 26

Where does the spinal cord end at birth?

Answer 26

About the level of the third of the third lumbar vertebral body.

Question 27

How are the spinal cord segments aligned compared to the vertebrae in the embryo?

Answer 27

The spinal cord segments are aligned to their corresponding vertebrae.

Question 28

What is the cauda equina?

Answer 28

Long dorsal and ventral roots that droop inferiorly and exit through lumbar and sacral intervertebral foramina.

Question 29

What is the conus medullaris?

Answer 29

Inferior portion of the spinal cord.