Lecture 3 - Spinal cord Flashcards
Where are vertebrae derived from
each vertebrae derived from a single somite
Spinal cord
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
Multiple spinal foramina
Spinal canal
Intervertebral foramina
Spinal nerves leave the spinal canal via the intervertebral foramina
Cauda equine
Spinal nerves in the spinal canal
Where do the cervical spinal roots emerge
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
Except for the cervical spinal roots, where do the other spinal roots emerge from
Corresponding nerve roots exit inferior to the vertebral body
Where do the S5 and first coccygeal nerve root exit from
Sacral hiatus
Rami
Branches of the spinal nerve divided
Posterior (dorsal) ramus
Supplies the deep muscle and skin of the dorsal trunk
Small
Anterior (ventral) ramus
Supplies the muscle and skin of the upper and lower limbs and the lateral and ventral trunk
Larger
Meningeal branch
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.
Grey ramus communicans
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
Posterior (dorsal) rami divides
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
Ventral axial lines
Centre of ventral or dorsal compartments of the limb
Upper limb rotation
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
Lower limb rotation
Rotates internally (medially) 90 degrees
Future knees face anteriorly
Extensor muscles lie on the anterior aspect of the lower limb
Axial lines
Run down the centre of the limbs in the embryo
Mark the junction of 2 dermatomes from discontinuous spinal levels
Axial borders
Cephalic and caudal margins of the limb bud
Mark the borders of the anterior and posterior compartments of the limb
Position of axial border after upper limb rotation
Pre axial - lie on the lateral side of the arm
Therefore thumb lies laterally
Post axial - lies on the medial side of the arm
Axial borders after lower limb rotation
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
What marks the pre axial border in the upper limb
Cephalic vein
What marks the post-axial border in the upper limb
Basilica vein
Lower limb marker for pre-axial border
Great saphenous vein
Lower limb marker for post-axial border
Small saphenous vein
anterior rami
Ventral
C5-T1
Brachial plexus
Supply muscles and skin of the upper limb
Posterior rami
Dorsal
L1-S5
Lumbosacral plexus
Supplies muscles and skin of lower limb
Plexuses
Complex networks of nerves that divide and merge with other bundle of nerve fibres multiple times
Musculocutaneous nerve
C5 , C6 , C7 spinal nerves
Supplies the skin of the lateral forearm
Femoral nerve
Fibres from L3 and L4 spinal nerves
L4 dermatome = saphenous branch of the femoral nerve
L3 = anterior and lateral femoral cutaneous nerve
Peripheral nerves
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
Myotome
Group of muscles supplied by a single spinal nerve
Motor unit
Motor neurone and the skeletal muscles fibre it innervates
