MSK Session 4 (Lecture 4.1)

Question 1

What is the adult nervous supply to the dermis and muscle of a dermatomyotome?

Answer 1

Spinal segmental nerve

Question 2

Where does the spinal cord start?

Answer 2

Medulla in the brain

Question 3

Where does the spinal cord end?

Answer 3

Ends at conus medullaris where it forms a ligament = filum terminale.

Ends around L2/L3

Question 4

What are the two important features of a vertebrae in relation to the spinal cord?

Answer 4

1) Vertebral foramen

2) Inter-vertebral foramen

Question 5

Where does the S.C run through the vertebral column? What does it form?

Answer 5

Vertebral foramina forming spinal canal

Question 6

What does the spinal cord give off through the inter-vertebral foramina?

Answer 6

Pair of right and left nerves at each vertebral level called spinal nerves.

Question 7

What are the spinal nerves also known as?

Answer 7

Segmental nerves

Question 8

What is special about the spinal nerves emerging in the cervical spine?

Answer 8

S.N. emerge superior to their corresponding vertebral level.

Question 9

What is special about the spinal nerves emerging in the non-cervical spine?

Answer 9

S.N. emerge inferior to their corresponding vertebral level.

Question 10

What are the levels of the spinal cord including numbers?

Answer 10

C1-7
T1-T12
L1-L5
S1-S5
Coccygeal root

Question 11

What is a neural level?

Answer 11

Segment of nerve tissue emerging from the spinal cord. I.E. the nerve level (NOT VERTEBRAL LEVEL)

Question 12

Where are the two enlargements of the spinal cord?

Answer 12

Cervical and lumbar bulges

Question 13

What are segmental nerves also known as?

Answer 13

Mixed spinal nerves

Question 14

What does each spinal segmental nerve comprise of?

Answer 14

1) Dorsal roots (sensory or afferent)

2) Ventral roots (efferent) - motor (skeletal muscle) and autonomic (smooth muscle, glands)

Question 15

What is a ramus?

Answer 15

Branch

Question 16

What is the difference between the size of the dorsal and ventral rami?

Answer 16

Dorsal (posterior) is smaller while to ventral (anterior) is larger

Question 17

What does the dorsal ramus divide into?

Answer 17

Medial and lateral branches

Question 18

Which spinal segments supply the lower limb?

Answer 18

Lumbar and Sacral (L1-S4)

Question 19

What are the two separate network of nerves that supply the lower limb?

Answer 19

Lumbar plexus (L1-L4) and Sacral plexus (L4-S4)

Question 20

Where does the lumbar plexus form?

Answer 20

Behind the psoas major muscle

Question 21

Where do the nerves emerge from the lumbar plexus?

Answer 21

Medial or lateral to the borders of the psoas major muscle.

Question 22

What are the nerves emerging lateral to psoas?

Answer 22

Femoral (L2-L4)
Iliohypogastric
Ilioinguinal
Lateral cutaneous nerve of the thigh

Question 23

What are the nerves emerging medial to psoas?

Answer 23

Obturator nerve

Lumbrosacral

Question 24

What is the sacral plexus composed of?

Answer 24

Lumbosacral trunk (half of L4 & all L5)
Sacral spinal segmental outflow

Question 25

Where does the sacral plexus form? Where does it lie in relation to?

Answer 25

Pelvic cavity

Lies in relation to piriformis

Question 26

What does the sacral plexus supply?

Answer 26

Pelvic region
Gluteal region
Perineal region
Lower limb via sciatic nerve

Question 27

What is a dermatome?

Answer 27

Area of skin supplied by sensory nerve fibres from a single spinal nerve (neural level)

Question 28

Which part of the body does not have a dermatome?

Answer 28

Anterior face (supplied by a CN)

Question 29

Why is overlap of dermatomes useful?

Answer 29

Damage to 1 nerve does not render loss of function to the area.

Also reduces probability of skin patches without natural sensory nerve supply

Question 30

What is the axial line?

Answer 30

Line of junction of two dermatomes supplied from discontinuous spinal levels

Question 31

Where are the axial lines marked on the upper and lower limb?

Answer 31

Upper - cephalic & basilic veins

Lower - great saphenous & small saphenous veins

Question 32

What are sensory nerve territories?

Answer 32

Sensory divisions of terminal nerves of the brachial plexus supply the skin in territorial domains