Plexus Flashcards
What nerves contribute to the phrenic nerve? What does it do?
VPR C3, C4, and C5
Mostly C4
Motor innervation to the diaphragm (phrenic nerves are bilateral)
Also innervates pericardium
What nerves make up the ansa cervicalis? (Superior and inferior root) What does it do?
Ansa cervicalis provides MOTOR innervation to anterior and lateral deep neck muscles.
Superior root formed from VPR C1-C2
Inferior root formed from VPR C2-C3
What does the Greater occipital nerve do and where does it originate?
Innervates skin over the posterior occipital region
Comes from DPR C2
What does the Lesser occipital nerve do and from where does it originate?
Innervates skin of superior posterolateral neck, and scalp posterior to external ear/pinna (more lateral occipital region)
Comes from VPR C2
Where does the spinal cord technically end in the vertebral column?
Leaves through foramen magnum beginning as an extension of the medulla oblogata
Ends at conus medullaris at L1/L2
Conus medullaris terminates variably from T12-L3
Where are the two enlargements in the spinal cord and what are they for?
Enlargements are for allowing attachment for nerves/plexuses that supply the limbs
Cervical enlargement: C4-T1, major part is brachial plexus which innervates upper extremity
Lumbosacral enlargement: L1-S1, lumbar and sacral plexuses, innervates lower extremities
What vessels supply blood to the spinal chord? (2 main ones)
Anterior spinal artery: midline, longitudinal
Formed by mostly vertebral arteries, also thyrocervical trunk and costocervical trunk from ascending cervical and deep cervica respectively
Posterior spinal artery: bilateral, longitudinal
Formed by mostly vertebral arteries and posterior inferior cerebellum artery, also contributing branches from ascending cervical and deep cervical
Where is the cervical plexus located relative to muscles in the neck?
It is sandwiched
Deep to the SCM
Superficial to the levator scapulae and middle scalene
What is unique about C1 contribution to the cervical plexus?
C1 and C2 for the superior root of ansa cervicalis, but C1 is lazy so it’s C2 that actually sends a branch up to C1
C1 sends its brach alongside the hypoglossal nerve
C1 has no VPR
Only has DPR - innervates intrinsic neck/head muscles
No cutaneous innervation so no C1 dermatome
Where does the 3rd Occipital nerve branch from?
DPR C3 for intrinsic nuchal muscles
What sensory branches of the cervical plexus innervate the anterior and lateral neck sensation?
Lesser occipital C2
Great auricular C2, C3
Transverse Cervical C2, C3 (sensory to anterior neck)
Supraclavicular (medial, intermediate, lateral) C3, C4 (sensory to superolateral shoulder)
Ansa cervicalis motor branches innervate all infrahyoid muscles except _____?
Thyroidhyoid (which is instead innervated by C1 via the hypoglossal nerve)
Explain “lateral less, medial more” for the pectoral nerves location
Medial nerve pierces BOTH pectorals
Lateral nerve only pierces pectoralis MAJOR
Medial pectoral nerve comes from C8, T1
Lateral pectoral nerve comes from C5, C6, C7
Where does the long thoracic nerve come from and what does it do?
Comes from brachial plexus VPR C5-C7 (roots)
Innervates serratus anterior, resting on the outer surface (nerve descends posterior to brachial plexus and axillary vessels)
