Spinal Nerves andSpinal PlexusesSLIDES 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 PlexusesThe 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 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• 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.