ANAT 215 Study Guide - Dorsal Root Ganglion, Preganglionic Nerve Fibers, Lateral Rectus Muscle

• School: Queen's University
• Department: Anatomy and Cell Biology
• Course: ANAT 215
• Professor: Leslie W Mac Kenzie

Document Summary

There are 31 pairs of spinal nerves: 8 cervical spinal nerves, 12 thoracic, 5 lum- bar, 5 sacral, and 1 coccygeal spinal nerve. Each can be identified by its associa- tion with adjacent vertebrae. cervical nerves take their names from the vertebra immediately following them. Spinal nerves caudal to the first thoracic vertebra take their names from the vertebra immediately preceding them. Thus, the spinal nerve t1 emerges immediately caudal to vertebra t1, spinal nerve t2 follows vertebra t2, and so forth. All spinal nerves form two branches, a dorsal ramus and a ventral ramus. Because preganglionic axons are myelinated, the branch carrying those fibers to the ganglion has a light color, and it is known as the white ramus (ramus, branch): two groups of unmyelinated postganglionic fibers leave the ganglion. Those innervating glands and smooth muscles in the body wall or limbs form a second branch, the gray ramus, that rejoins the spinal nerve.