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Spinal Nerves. Spinal nerves. 31 pairs arise from spinal cord Five groups correspond to regions of spinal cord and vertebrae Cervical 8 pr. Thoracic 12 pr. Lumbar 5 pr. Sacral 5 pr. Coccygeal 1 pr. Structure of a Nerve. Bundle of axons Layers of connective tissue Epineurium
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Spinal nerves • 31 pairs arise from spinal cord • Five groups correspond to regions of spinal cord and vertebrae • Cervical 8 pr. • Thoracic 12 pr. • Lumbar 5 pr. • Sacral 5 pr. • Coccygeal 1 pr.
Structure of a Nerve • Bundle of axons • Layers of connective tissue • Epineurium • Perineurium • Endoneurium
Structure of a spinal nerve • Tree analogy • Dorsal root & ventral root fuse lateral to dorsal root ganglion • Whole nerve "trunk" lies in intervertebral foramen
Structure of a spinal nerve • Branches • Dorsal ramus • Ventral ramus • Communicating rami to sympathetic chain ganglion (ANS)
Spinal Nerve Plexuses • Ventral rami of spinal nerves fuse and form networks with ventral rami of other spinal nerves. • Crossing of fibers • A peripheral nerve may contain axons from several spinal segments. • T2 – T12 do not form plexuses
Spinal Nerve Plexuses • Cervical plexus • Brachial plexus • Lumbar plexus • Sacral plexus
Cervical plexus • C1 – C4 (+ C5) • cutaneous nerves, mostly sensory from skin of neck & back of head • Phrenic nerve to diaphragm • Motor stimulation for breathing!
Brachial plexus • C5 – T1 • Complex fusion, splitting, fusion, & division into nerves • Axillary Nerve • to deltoid • Musculocutaneous nerve • to biceps brachii, brachialis
Brachial plexus • Radial nerve • to triceps brachii, extensors of wrist, hand, fingers • Wrist drop • Median nerve • to flexors of wrist, hand, fingers • can be compressed • Carpal Tunnel Syndrome • Ulnar nerve • (“funny bone”) • to flexors in hand • “Claw hand”
Lumbar plexus • L1 – L4 (+ L5) • Ilioinguinal nerve • mostly sensory from skin of thigh & genitals • Genitofemoral nerve • mostly sensory from scrotum, labia majora, ant. Thigh • Femoral Nerve • to quadriceps, sartorius
Sacral plexus • L4 – S4 • Superior & inferior gluteal nerves • To gluteus muscles • Sciatic nerve • To hamstrings & other posterior thigh & leg muscles • Pudendal nerve • Sensory from penis, clitoris, labia minora, anus