Spinal nerves & plexuses Flashcards
How many spinal nerves are there?
31 pairs
How are the spinal nerves named?
For the vertebrae at the level of the spinal cord where they originate
List the number of spinal nerves in each area of the spinal cord
8 cervical
12 thoracic
5 lumbar
5 sacral
1coccygeal
where do the spinal nerves emerge?
Through the intervertebral foramina; for the sacral nerves, through the 5 sacral foramina
Where does the first cervical nerve emerge?
Between C1 and the occipital bone
Where does the 8th cervical nerve emerge?
Between C7 and T1
Where do the lumbar and thoracic nerves and C2-C7 nerves emerge?
Between the vertebra sharing its designation with the nerve and the next (inferior) vertebra
What is a nerve plexus?
A rearrangement of spinal nerve axons to serve specific body areas/functions
how many spinal nerve plexuses are there?
4
This plexus is served by nerves C1-C5 and innervates the posterior head and neck
Cervical plexus
This nerve connects to the diaphragm and is in the cervical plexus
Phrenic nerve
This plexus is served by C4-T1 and innervates the upper limbs
Brachial plexus
This nerve is the large nerve of the brachial plexus that branches into the axillary nerve (armpit)
Radial nerve
Name the nerves that travel down the arm
Radial nerve, ulnar nerve, median nerve
This plexus is served by the ventral rami of T12-L4 and innervated the pelvic region and anterior leg
Lumbar plexus
This is the major nerve of the lumbar plexus that branches into the saphenous nerve of the anterior lower leg
Femoral nerve
This plexus is served by L4-5 and S1-S4 and innervates the posterior leg and foot
Sacral plexus
This is the large nerve of the sacral plexus that travels across the hip and down the leg
Sciatic nerve
These are the nerves that combine into the sciatic nerve
tibial nerve, fibular nerve
This plexus is formed by the thoracic nerves
Thoracic nerves are NOT part of a plexus–they emerge to create the intercostal nerves
How do plexuses form?
By fusion of ventral rami during development
What is the purpose of plexuses?
Redundant innervation of the limbs
What is the dermatome?
Map of innervated sensory regions
Describe the cervical plexus
Ventral rami of C1-C5
Neck, thoracic cavity, diaphragm
Major nerve: phrenic (controls diaphragm)
Describe the brachial plexus
Ventral rami of C5-T1
Pectoral girdle & arms
Major nerves: musculocutaneous, axillary, median, radial, ulnar
Describe the lumbar plexus
Ventral rami of T12-L4
Pelvic girdle & leg (upper & anterior)
Major nerves: femoral, obturator
Describe the sacral plexus
Ventral rami of L4-S4
pelvic girdle & leg (hammies, lower leg)
Major nerves: Sciatic, tibial, common, fibular
