Lecture 3 - Spinal cord

Question 1

Where are vertebrae derived from

Answer 1

each vertebrae derived from a single somite

Question 2

Spinal cord

Answer 2

Commences at the inferior margin of the medulla oblongata at the base of the brain stem

Ends at the conus medullaris at L2

Runs through spinal foramina

Spinal cord does not completely fill the length of the vertebrae canal

Question 3

Multiple spinal foramina

Answer 3

Spinal canal

Question 4

Intervertebral foramina

Answer 4

Spinal nerves leave the spinal canal via the intervertebral foramina

Question 5

Cauda equine

Answer 5

Spinal nerves in the spinal canal

Question 6

Where do the cervical spinal roots emerge

Answer 6

Above the corresponding vertebral body
Exception of the 8th cervical spinal root - emerges between C7 and T1

As there are 8 cervical spinal roots but only 7 cervical vertebrae

Question 7

Except for the cervical spinal roots, where do the other spinal roots emerge from

Answer 7

Corresponding nerve roots exit inferior to the vertebral body

Question 8

Where do the S5 and first coccygeal nerve root exit from

Answer 8

Sacral hiatus

Question 9

Rami

Answer 9

Branches of the spinal nerve divided

Question 10

Posterior (dorsal) ramus

Answer 10

Supplies the deep muscle and skin of the dorsal trunk

Small

Question 11

Anterior (ventral) ramus

Answer 11

Supplies the muscle and skin of the upper and lower limbs and the lateral and ventral trunk

Larger

Question 12

Meningeal branch

Answer 12

Tiny
Re enters the spinal canal through the intervertebral foramen
Each spinal nerve also branches into a meningeal branch

Supplies the vertebrae, ligaments of the vertebral column, blood vessels and meninges.

Question 13

Grey ramus communicans

Answer 13

Spinal nerve receives a grey ramus communicans branch from adjacent paravertebral ganglion of the sympathetic trunk

Contain post ganglionic nerve fibres of the ANS - unmyelinated

Question 14

Posterior (dorsal) rami divides

Answer 14

Into medial and lateral branches that supply the skin of the back in a tidy segmental manner

Each dorsal ramus supplies a narrow strip of muscle and skin in line with the intervertebral foramen

Question 15

Ventral axial lines

Answer 15

Centre of ventral or dorsal compartments of the limb

Question 16

Upper limb rotation

Answer 16

Rotates externally (laterally) 90 degrees on its longitudinal axis

Future elbow points backwards (posterially)
Extensor muscles lie on the lateral and posterior aspects of the limb

Question 17

Lower limb rotation

Answer 17

Rotates internally (medially) 90 degrees

Future knees face anteriorly
Extensor muscles lie on the anterior aspect of the lower limb

Question 18

Axial lines

Answer 18

Run down the centre of the limbs in the embryo

Mark the junction of 2 dermatomes from discontinuous spinal levels

Question 19

Axial borders

Answer 19

Cephalic and caudal margins of the limb bud

Mark the borders of the anterior and posterior compartments of the limb

Question 20

Position of axial border after upper limb rotation

Answer 20

Pre axial - lie on the lateral side of the arm

Therefore thumb lies laterally

Post axial - lies on the medial side of the arm

Question 21

Axial borders after lower limb rotation

Answer 21

Pre-axial - lies on the anteromedial aspect of the limb

Post-axial - lies on the posterior (posterolateral) aspect of the limb

Therefore the great toe lies medially

Question 22

What marks the pre axial border in the upper limb

Answer 22

Cephalic vein

Question 23

What marks the post-axial border in the upper limb

Answer 23

Basilica vein

Question 24

Lower limb marker for pre-axial border

Answer 24

Great saphenous vein

Question 25

Lower limb marker for post-axial border

Answer 25

Small saphenous vein

Question 26

anterior rami

Answer 26

Ventral
C5-T1
Brachial plexus
Supply muscles and skin of the upper limb

Question 27

Posterior rami

Answer 27

Dorsal
L1-S5
Lumbosacral plexus
Supplies muscles and skin of lower limb

Question 28

Plexuses

Answer 28

Complex networks of nerves that divide and merge with other bundle of nerve fibres multiple times

Question 29

Musculocutaneous nerve

Answer 29

C5 , C6 , C7 spinal nerves

Supplies the skin of the lateral forearm

Question 30

Femoral nerve

Answer 30

Fibres from L3 and L4 spinal nerves

L4 dermatome = saphenous branch of the femoral nerve

L3 = anterior and lateral femoral cutaneous nerve

Question 31

Peripheral nerves

Answer 31

Contain fibres from one or more spinal nerves

Area of skin supplied by peripheral nerve does not correspond to the dermatome map as the peripheral nerve contains fibres from multiple dermatomes

Dermatome may be supplied by more than one peripheral nerves

Question 32

Myotome

Answer 32

Group of muscles supplied by a single spinal nerve

Question 33

Motor unit

Answer 33

Motor neurone and the skeletal muscles fibre it innervates