Spinal Nerves and Spinal Plexuses

SLIDES AND NARRATION BY MARY KLINGER

Nerve Plexuses

•Complex, interwoven networks of nerve fibers

•Formed by blended fibers of ventral rami of adjacent spinal nerves

•Mixed nerves.

•Control muscles of the neck and upper and lower extremities

•Receive sensory information from skin superficial to muscles.

Nerve Plexuses

The four major plexuses made from ventral rami

1. Cervical plexus

2. Brachial plexus

3. Lumbar plexus

4. Sacral plexus

Nerve Plexuses

•Cervical Plexus▫Includes ventral rami of spinal nerves C1 –

C5

▫Innervates muscles of the neck, thoracic cavity and diaphragm

▫Major nerve Phrenic nerve - innervates the diaphragm and

contains fibers from C3, C4, and C5.

Nerve Plexuses•Picture of cervical plexus in situ:

Nerve Plexuses•Brachial Plexus

▫Includes ventral rami of spinal nerve roots C5 – T1

▫Innervates pectoral girdle and upper limbs

▫Nerves that form brachial plexus originate from Superior, middle, and inferior trunks Anterior and posterior divisions Lateral, medial , and anterior cords Smaller branches or named nerves, innervate

muscles

Nerve Plexuses•Brachial Plexus

▫Major nerves of brachial plexus Musculocutaneous nerve – innervates biceps

brachii Median nerve – innervates most flexors of the

forearm Ulnar nerve – innervates medial portions of

the hand Axillary nerve – innervates the deltoid Radial nerve – innervates most extensors of

the arm and forearm

Nerve PlexusesPicture of Brachial Plexus in Situ

Nerve Plexuses• Picture of brachial plexus

Nerve Plexuses•Lumbar Plexus

▫Includes ventral rami of spinal nerves T12 – L4

▫Major nerves Obturator nerve – innervates the adductors of

the hip Femoral nerve - innervates the quadriceps

femoris muscle group

Nerve Plexuses

Picture of Lumbar Plexus

Nerve Plexuses•Sacral Plexus

▫Includes ventral rami of spinal nerves L4 – S4

▫Major nerve Sciatic nerve – longest and largest nerve in the

PNS Innervates the flexors of the knee and foot Branches into

▫Fibular nerve – innervates part of the hamstrings and anterior tibialis m.

▫Tibial nerve – innervates part of the hamstrings and the gastrocnemius and soleus mm.

Nerve Plexuses

Picture of the Sacral plexus