Lippincotts 5 - Spinal Cord

Question 1

how is the spinal cord divided?

Answer 1

the spinal cord is divided into 31 segments, and a pair of spinal nerves is associated with each segment:

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

each spinal nerve contains both sensory and motor information

Question 2

in cross section, how is the spinal cord organised?

Answer 2

throughout the spinal cord the distribution of grey matter is butterfly shaped.
the grey matter is surrounded by white matter.

each side there is an anterior and a posterior horn.
also a lateral horn, at sympathetic and parasympathetic levels, (T1-L2, S2-S4)

Question 3

how does the spinal cord grow?

Answer 3

as a newborn the spinal cord reaches the level of vertebra L3.

the vertebral canal grows to a greater extent than the spinal cord, and so in adults the spinal cord extends to the L1-L2 level in the vertebral column.

Question 4

where are the two major enlargements in the spinal cord? - what are they for?

Answer 4

1. cervical
2. lumbar

enlargements are where neurons supplying plexuses for the upper and lower limbs are located.

Question 5

where does the spinal cord end?

where is it attached?

Answer 5

the spinal cord ends at the conus medullaris and is attached to the dorsum of the coccygeal segment by the filum terminale.

Question 6

what are the longitudinal fissures and sulci marked on the spinal cord?

Answer 6

1. anterior median fissure
2. posterior median sulcus and septum
3. posterolateral sulcus
4. anterolateral sulcus

Question 7

what is the anterior median fissure?

Answer 7

the anterior median fissure is apparent the entire length of the spinal cord.
the anterior spinal artery runs its length and is found within the subarachnoid space.
deep to the anterior median fissure is the anterior white commissure where some fibres cross the midline.

Question 8

what is the posterolateral sulcus?

Answer 8

the posterolateral sulcus is the entry point of posterior sensory rootlets.

Question 9

what is the anterolateral sulcus?

Answer 9

the anterolateral sulcus is the entry point of anterior motor rootlets

Question 10

what are the elevations between the longitudinal fissures and sulci called in the spinal cord?

Answer 10

funiculi

funiculi are where descending and ascending tracts of the spinal cord are found

Question 11

what are funiculi?

Answer 11

elevations in the spinal cord

funiculi are where descending and ascending tracts of the spinal cord are found

Question 12

where is the posterior column of the spinal cord found?

Answer 12

the posterior column of the spinal cord is located bilaterally between the posterior median sulcus and the posterolateral sulcus.

Question 13

where is the lateral column of the spinal cord found?

Answer 13

the lateral column of th spinal cord is found between the posterolateral and anterolateral sulci.

Question 14

where is the anterior column of the spinal cord found?

Answer 14

the anterior column of the spinal cord is found between the anterior median fissure and the anterolateral sulcus.

Question 15

what is found in the posterior column of the spinal cord?

Answer 15

the posterior column of the spinal cord in the cervical and upper thoracic regions is divided into tracts carrying sensory information up the spinal cord to the medulla.

- fasciculus gracilis: lower trunk and lower limbs
- fasciculus cuneatus: upper trunk and upper limbs

Question 16

what is found in the lateral column of the spinal cord?

- tracts

Answer 16

the lateral column of the spinal cord holds the main motor tract if the spinal cord (lateral corticospinal tract) descending from the forebrain, having crossed the brainstem to reach Lower Motor Neurons at each spinal cord level.

1. lateral corticospinal tract: medial, adjacent to grey matter.
2. spinocerebellar tract: lateral to corticospinal tract (proprioception)
3. spinothalamic tract: anterior part of lateral column (pain and temp)

Question 17

what is found in the anterior column of the spinal cord?

Answer 17

the main tract in the anterior column is the anterior corticospinal tract. it lies medially and carrys motor information from the cortex to the LMNs.

other tracts include the vestibulospinal tract and the reticulospinal tract (descending motor tracts)

Question 18

what is the internal structure of the spinal cord?

Answer 18

in the spinal cord, the grey matter in loacated centrally with white surrounding it.
grey matter contains the nerve cell bodies:
- anterior horn: motor neurons and interneuron circuits
- posterior horn: sensory neurons
- lateral horn: T1-L2, S2-S4 (ANS)

white matter is divided into 3 columns:
- anterior, lateral and posterior

Question 19

what are a the subdivisions of grey matter in the spinal cord?

Answer 19

the grey matter can be divided into 10 distinct segments, rexed laminae I-X

• layers I to VI comprise the posterior horn
• layers VII to IX comporis the anterior horn
• Layer X surrounds the central canal

Question 20

what are the specific subnuclei of grey matter in the spinal cord?

Answer 20

posterior horn:

• substantia gelatinosa: lamina II (pain and temp)
• nucleus proprius: laminae III and IV
• Clarke nucleus

lateral horn:
- intermediolateral nucleus

anterior horn:
- special motor nuclei

Question 21

what is the clarke nucleus?

Answer 21

the clarke nucleus is a specialised nucleus found in the spinal cord from C8 to L3.

the clarke nucleus is an important relay station for nonconscious proprioception going to the cerebellum.

proprioceptive fibres above C8 travel in the fasciculus cuneatus up to the medulla.

proprioceptive fibres below L3 run in the fasciculus gracilis to L3 where they synapse with the clarke nucleus.

Question 22

what are the sources of blood supply to the spinal cord?

how do they supply the spinal cord?

Answer 22

the blood supply to the spinal cord comes from two sources:

1. vertebral-basilar system
2. segmental arteries

a branch from each vertebral artery joins to form the anterior spinal artery, which runs in the anterior median fissure.