Dermatomes and Myotomes

Question 0

Define motor unit

Answer 0

Muscle fibres innervated by a single motor nerve fibre

Question 1

Define dermatomyotome

Answer 1

Embryonic precursors of the dermis and muscle units. Differentiate into dermatome and myotome

Question 2

Which part of the spinal cord has segmental nerves which emerge superiorly to the corresponding vertebral level?

Answer 2

The cervical cord

Question 3

Give the regions of the spinal cord and the number each region goes up to

Answer 3

Cervical - C1-C7
Thoracic - T1-T12
Lumbar - L1-L5
Sacral - S1-S4

Question 4

What are the efferent and afferent roots given out by each spinal segment nerves?

Answer 4

Dorsal roots are afferent
Ventral roots are efferent
(DA, VE)

Question 5

What functions do ventral roots have?

Answer 5

Motor (skeletal muscle)

Autonomic (smooth muscle and glands)

Question 6

Explain how a mixed segmental nerve divides once it has emerged from the intervertebral foramen

Answer 6

(Dorsal and ventral converge to form a mixed segmental nerve)
Splits into posterior and anterior rami
Posterior ramus divides into medial and lateral branches

Question 7

Which roots make up the lumbar plexus?

Answer 7

L1-L4

Question 8

Which roots make up the sacral plexus?

Answer 8

L4-S4

Question 9

Where is the lumbar plexus?

Answer 9

Behind the psoas major muscle

Question 10

Which nerves emerge from the lumbar plexus lateral to psoas major?

Answer 10

Femoral
Iliohypogastric
Ilioinguinal
Lateral cutaneous of thigh

Question 11

Which nerves emerge medial to psoas major from the lumbar plexus?

Answer 11

Obturator

Lumbksacral trunk

Question 12

Where is the sacral plexus?

Answer 12

In the pelvic cavity

Question 13

What does the sacral plexus supply?

Answer 13

Pelvic, gluteal and perineal regions

Lower limb via the sciatic nerve

Question 14

What is a sensory nerve territory?

Answer 14

Cutaneous distribution of peripheral nerve.
Area of skin that the peripheral nerve innervates.
Can have nerve fibres from several spinal roots.

Question 15

Which myotome is flexion of the forearm predominantly done by?

Answer 15

C6

Question 16

Which myotome is extension of the forearm at the elbow predominantly done by?

Answer 16

C7

Question 17

Which myotome is flexion of the fingers mostly controlled by?

Answer 17

C8

Question 18

Which myotome is abduction and adduction of the fingers controlled by?

Answer 18

T1

Question 19

Which myotomes is flexion of the hip controlled by?

Answer 19

L1 and L2

Question 20

Which myotomes is extension of the knee controlled by?

Answer 20

L3 and L4

Question 21

Which myotomes is flexion of the knee controlled by?

Answer 21

L5-S2

Question 22

Which myotomes is plantarflexion of the foot controlled by?

Answer 22

S1 and S2

Question 23

A tap on the biceps tendon in the cubital fossa tests which spinal cord level?

Answer 23

C6

Question 24

Tapping the tendon of the triceps on the posterior tendon tests which spinal root?

Answer 24

C7

Question 25

A tap on the patellar ligament test which spinal roots?

Answer 25

L3 and L4

Question 26

A tap on the calcaneal tendon posterior to the ankle tests which spinal roots?

Answer 26

S1 and S2