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 Lab Manual - Deep Back & Spinal Cord

Learning Objectives:

Upon completion of this session, the student will be able to:

  1. Identify and give the function of the significant parts of a typical vertebra and associated ligaments. (explanation)
  2. Identify the specialized vertebrae. (explanation)
  3. Describe the spine, its curvatures, and vertebral column movements. (explanation)
  4. Identify the coverings and the supporting structures of the spinal cord. Give the point of the termination of the spinal cord and the dural sac. (explanation)
  5. Identify the terminal specialties of the cord, their relation to lumbar puncture, the nerve rootlets, and blood supply. (explanation)
  6. Describe the anatomy of the cord and vertebrae as related to fractures, dislocations, and possible cord injury. (explanation)
  7. Describe or illustrate the location and function of the basic somatic motor and sensory neurons on a cross section of the spinal cord. (explanation)
  8. Describe a typical spinal nerve, the somatic motor and sensory components found in any portion, and their distribution. (explanation)
  9. Describe conceptually how any region of the thoracic wall gets its blood supply and innervation. (explanation)
  10. Define and explain the significance of dermatomes. (explanation)
  11. Explain the difference between superficial and deep (true) back muscles. (explanation)

Readings and Modules:

Procedure:

1. Review the bony landmarks. (Play movie; View images: N 17, 159, 153a, 153b, 155, 157, 158, 159, TG 1-02, 1-03A, 1-03D, 1-05A, 1-05B, 1-05D, 1-08A, 1-08B, 1-10, 1-11A, 1-11B)

Examine a thoracic vertebra and identify: body, vertebral arch (spinous process, lamina, pedicle, transverse process, superior and inferior articular processes), vertebral foramen (enclosed by body and arch). Examine vertebrae of other regions; note similarities or differences as well as the specialized vertebrae: atlas, axis, sacrum, coccyx. Consider the vertebral column as a whole and the structures which unite it: supraspinous ligament, ligamentum flavum, posterior longitudinal ligament, anterior longitudinal ligament (will be seen later), intervertebral disc. Identify intervertebral foramina, superior and inferior vertebral notches, and anterior and posterior sacral foramina.

Lumbar Spine Zoom Intervertebral disc and spinal cord
Lumbar Cross Zoom Intervertebral foramina
lumbar Spine Zoom Intervertebral foramina with spinal nerves
CT of L3
Lumbar spine

2. Move the deep back muscles laterally. (Play movie; View images: N 174, 175, 176, 424, TG 1-13, 1-14, 1-15, 2-07)

Reflect the serratus posterior superior and inferior muscles and the thoracolumbar aponeurosis. If you do not see the serratus muscles, they may have been reflected with the rhomboids and latissimus dorsi, which is fine. The deep back muscles, including the erector spinae muscle, must be moved laterally in order to expose the posterior aspect of the vertebral column. These muscles are very complex and identification of their various parts is not necessary. Using the scalpel, make a deep incision just lateral to the vertebral spinous processes from the tip of the coccyx up to the occipital protuberance. Next, insert the chisel in this incision and pull the deep back muscles (the parallel columns of muscles on either side of the spinous processes) laterally away from the vertebrae. Pull these muscles laterally until ample space is present to see the features of the vertebral column. In the cervical region, leave the levator scapulae in place. Retain the dorsal primary rami of some exemplary spinal nerves in order that their continuity with the spinal nerve and spinal cord can be established.

3. Using a chisel and mallet remove the spinous processes and laminae from the length of the vertebral column. (Play movie; View images: N 155, 157, 158, 159, TG 1-08, 1-11A, 1-11B)

Using a chisel and hammer remove the posterior wall of the vertebral canal from the base of the skull to the sacrum. Remove the spine and laminae in 2 or 3 vertebrae to establish the size of the spinal vertebral canal. Then chisel (remove) toward the head and sacrum pointing the chisel at the junction of the lamina and the transverse process. In this procedure remove as many adjacent laminae together as possible to see the ligamentum flavum; these are most easily observed in the thoracic region. Remove the posterior sacral laminae. Special care should be taken on the dorsum of the sacrum since the spines are short and the laminae thin. Identify the hiatus of the sacral canal. Widen the opening of the spinal canal by trimming the laminae with bone forceps.

4. Open the dura mater and identify the features of the meninges, spinal cord and spinal nerve roots. (Play movie; View images: N 136, 138, 139, 158, 160, 161, 169, 170, 171, 172 a+b, 173, 180, 258, TG 1-18, 1-19, 1-20, 1-21, 1-22)

With the vertebral canal open, examine the epidural fat and the vertebral venous plexuses. Remove the epidural fat and examine the dura mater, noting shape and size (in relation to size of spinal canal), and termination at the level of the second sacral vertebra (S2). Look for the coccygeal ligament. What is it? Answer Note lateral continuities of the dura at the intervertebral foramen (covering what? Answer), dorsal root ganglion and attachment of dura to intervertebral foramen. Identify the dorsal root ganglion, the spinal nerve, and dorsal and ventral primary rami of exemplary nerves. Open the dura mater by a mid-line incision, taking care to avoid cutting through the arachnoid mater lying just deep and adhering to the dura. Identify the potential subdural space.

Explore the subarachnoid space. Note arachnoid trabeculae. What does the subarachnoid space contain? With what is it continuous? Answer

Observe the spinal cord. Note its covering, the pia mater (inseparable from cord) and its specializations: the filum terminale (where does it lie, where does it attach? Answer), the denticulate ligament and denticulations (what are their relations to the roots of spinal nerve? Answer How many denticulations? Answer Where do they attach? Answer).

On the spinal cord, observe the size, cervical and lumbar enlargements, length, and sulci (anterior median fissure, posterior median sulcus), conus medullaris, and its point of termination at L2 (second lumbar vertebral level, or L1/L2 disc level). In newborns, the cord ends lower at L3. Answer

Using a sharp scalpel, cut through the spinal cord, reflect, and look for anterior and posterior spinal arteries. What are their sources? Answer What reinforces the spinal arteries? Answer Can you find any radicular arteries or veins. What are radicular arteries? Answer Are all radicular arteries the same? Answer What is the source for radicular arteries? Answer Observe arrangement of gray matter and white matter of the cord. What is their significance? Answer Review the significance of the ventral, lateral and dorsal horns of gray matter.

Reflect a portion of the dura lining the vertebral canal and expose the posterior longitudinal ligament in cervical and lumbar regions, note change of arrangement of the ligament in the lumbar area. Can you see the intervertebral disc? Answer Significance? Answer Relate to intervertebral foramen and spinal nerve.

Lumbar Myelogram AP Lumbar Myelogram Lateral Lumbar myelogram and spinal cord

5. Dissect out a spinal nerve laterally until it divides into primary rami. (Play movie; View images: N 160, 161, 169a+b, 170, 173, 192, 258, TG 1-09, 1-11A, 1-11B, 1-19, 1-20, 1-21, , 7-15, 7-56A, 7-56B)

In the thoracic region, dissect medially along one of the dorsal primary rami branches identified previously by cutting the deep back muscles that lay over it. Trace this dorsal ramus medially to the intervertebral foramen. Use the bone clippers to remove the bone from the posterior aspect of the intervertebral foramen, exposing the spinal nerve and the dorsal root ganglion. Where is the dura mater in relation to the intervertebral foramen? Answer Examine dorsal and ventral rootlets as they emerge from the cord. How is the segmental pattern created? AnswerTrace the dorsal and ventral rootlets from the spinal cord to the sleeve of dura mater containing the dorsal root ganglion. What is a root? Answer What is the functional difference between dorsal and ventral roots? Answer Are the roots in separate sheaths before uniting? Answer Where is the dorsal root ganglion? Answer What is the extent of the dura mater, arachnoid mater, and pia mater on the spinal nerves? Answer Trace the ventral primary ramus laterally for 5cm from the spinal nerve by carefully incising the intercostal muscles. Note the orientation of spinal roots and the cauda equina. Relate this to spinal (lumbar) puncture procedure.

 

Updated: 07 Sep 2011