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Search in Primal Pictures : ? embeddedcode=7D88D9 .The screen should show an image of the spinal cord. Label regions of the spinal cord: anterior horn, central canal, gray matter, lateral horn, posterior horn, white matter. 57 © 2011 Shirley J. Wright, Ph.D.
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PRE-LAB EXERCISE 4.7a: Spinal Nerve Structure Spinal nerves carry sensory and motor information and are thus mixed nerves . Each spinal nerve attaches to the spinal cord via two branches: a posterior root and an anterior root, with each root composed of 6-8 rootlets . Cell bodies of sensory afferents are located in a spinal ganglion (dorsal root ganglion) which appears as a swelling located in the posterior root, just before it joins the anterior root to form the spinal nerve. Incoming sensory afferents from the posterior root enter the spinal cord on its posterior side and synapse with neurons in the posterior horn of the gray matter. Thus, posterior roots carry sensory information to the posterior spinal cord. Cell bodies of motor efferents are located in the anterior horn of the spinal cord. Outgoing motor efferents exit the spinal cord on its anterior side via an anterior root, join the posterior root to form the spinal nerve, and exit through the intervertebral foramina. Thus, anterior roots carry motor information from the anterior spinal cord. Each spinal nerve soon splits into a posterior ramus (supplies intrinsic back muscles and skin associated with the muscles), and an anterior ramus (supplies skeletal muscles and skin of rest of body). Label the parts of the spinal nerve in the image below. 1 5 2 6 3 7 4 8 58 © 2011 Shirley J. Wright, Ph.D. 2 3 4 1 6 7 8 5
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PRE-LAB EXERCISE 4.7b: Histology of a Nerve There are two types of nerves: cranial nerves which exit the cranial cavity through foramina (holes) in the skull, and spinal nerves which exit the vertebral column through intervertebral foramina. Nerves can be different diameters. The sciatic nerve is one of the largest. Nerve diameter varies depending on the number of nerve fiber bundles (axons and their connective tissue) the nerve contains. Each axon (process of a single nerve cell that sends out signals) is wrapped in a myelin sheath which is surrounded by endoneurium composed of connective tissue. A nerve fiber is the axon plus its endoneurium cover and may or may not contain myelin (depends on the type of nerve). Bundles of nerve fibers are called nerve fascicles and they are wrapped in perineurium connective tissue. A nerve consists of many nerve fascicles that are wrapped in a fibrous connective tissue sheath called epineurium which also surrounds the outside of the nerve. Search in Primal Pictures : The screen at left should show spinal nerves and the spinal cord. Navigate through the different layers of the image. Label: epineurium, nerve fascicles, perineurium, nerve fibers, endoneurium, myelin sheath and axon in the images below.
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  • Spring '11
  • Masthay
  • Vertebra, Bones of the torso

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