Anatomy - Spinal Nerves and Segmental Innervation

Question 1

What is the only location where a spinal nerve is technically called a ‘spinal nerve’?

Answer 1

Intervertebral foramina

Question 2

There are 31 pairs of spinal nerves how are they split?

How are they named?

Answer 2

C1-C8
T1-T12
L1-L5
S1-S5
Co1

Cervical numbered - vertebrae below

All rest - vertebrae above

Question 3

Put in order from spinal cord to rami;

Root
Rootlets 
Spinal nerve
Posterior rami 
Anterior rami 

What is larger anterior or posterior rami?

Answer 3

Rootlets (posterior and anterior)
Roos
Spinal nerve (found in intervertebral foramen) 
Posterior rami 
Anterior rami

Anterior rami is larger and supplies anterolateral body wall

Question 4

Which types of axons pass through posterior roots and which through anterior roots?

Rami and spinal nerve carry both motor and sensory. T/F?

Answer 4

Posterior - sensory (stab in back)

Anterior - motor (move forward)

T - mixed modality

Question 5

Myotomes and dermatomes always line up. T/F?

Answer 5

F -

Question 6

What dermatome match the following landmarks - MUST know this:

• Nipple
• Umbilicus

Answer 6

Nipple - T4

Umbilicus - T10

Question 7

How many dorsal roots would be needed to be damaged to create dermatomal anaestsia?
Why?

Answer 7

3 - due to overlap of those above and below

Question 8

What do the heavier lines of the Foerster map mean?

Answer 8

No overlap of sensation from spinal nerves due to them not being continuous nerves e.g. T2 to L3

Question 9

Is it anterior or posterior rami that are involved in nerve plexuses?

Answer 9

Anterior only

Question 10

What is the difference between peripheral nerve cutaneous innervation and dermatome innervation?

Answer 10

Dermatome = area of skin supplied by single spinal nerve

Peripheral nerve = named nerve supplying area of muscle which can come from multiple spinal nerves