Prelab Images - Deep Back & Spinal Cord

Prelab should consist of reading the lab manual and dissector answers and viewing the dissection video. To begin your study, you may find it useful to look over the Netter's or LWW Atlas images listed below.

Step 1. Review the bony landmarks. (Play movie)

A thoracic vertebra is depicted in plate N154 or TG1-05. The vertebral arch is not labeled, but it is composed of 2 laminae and 2 pedicles, which are labeled. The spinous process, transverse process, superior articular process, and inferior articular process are all labeled. A lumbar vertebra can be seen in plate N155 or TG1-05. Cervical vertebrae are shown in plate N18 or TG1-03 with the atlas and axis shown in plate N17 or TG1-03. The sacrum and the coccyx are featured in plate N157 or TG1-08. Plate N153 or TG1-02 shows the whole spinal column. The supraspinous ligament, ligamentum flavum, posterior longitudinal ligament, anterior longitudinal ligament and intervertebral disk are all shown in plate N158 or TG1-11A (some are also labeled in N152 or TG1-11B). An intervertebral foramen is labeled in plates N158 or TG1-10 and N159 or TG1-11. Superior and inferior vertebral notches form the intervertebral foramen and are labeled in plate N154 or TG1-05. Plate N157 or TG1-08A and TG1-08B shows anterior and posterior sacral foramina.

Step 2. Move the deep back muscles laterally. (Play movie)

The serratus posterior superior and inferior and the thoracolumbar aponeurosis are shown in plate N174 or TG1-13 and TG1-14. Cut them near the spinous process where they attach and reflect them laterally. You should now be able to see the erector spinae muscle group labeled in plate N175 or TG1-14 (the scapula has been removed in this plate making it look different from your cadaver). Muscles deep to erector spinae are shown in plate N176 or TG1-15, but these will not be identified during the lab. Next, make a vertical cut just lateral to the spinous process from the coccyx up to the external occipital protuberance to create a slit in which the chisel can be inserted. Plate N424 or TG2-07 shows the levator scapulae arching up to the neck; try not to cut this muscle as it attaches to the transverse process of C1-C4. Also, try to save some of the dorsal primary rami you identified in the first lab by tracing them for a short distance into the back muscle before you use the chisel to pull these muscles away. Finally, use the chisel to try to pull the back muscles laterally 2-3 inches on both sides of the spinal cord away from the midline.

Step 3. Using a chisel and mallet remove the spinous processes and laminae from the length of the vertebral column. (Play movie)

Plate N155 or TG1-11 shows the lamina from the view you will see it in lab (the L3 and L4 vertebrae: posterior view picture). You want to use the chisel to chip through the laminae on both sides of the spinous process and then remove the spinous process to gain access to the spinal cord. The ligamentum flavum is shown in plate N158 or TG1-11A and TG1-11B. You will most likely see it stuck to the pieces of vertebrae you remove, like in the lower right picture of this plate. Plate N159 also shows the ligamentum flavum. The sacral hiatus is shown in plate N157 or TG1-08.

Step 4. Open the dura mater and identify the features of the meninges, spinal cord and spinal nerve roots. (Play movie)

The epidural fat is labeled in plate N170 or TG1-22 and the vertebral venous plexus can be seen embedded in this fat in plate N173 or TG1-22. This fat may be laying on the dura mater or may be removed with the spinous process. Plate N161 or TG1-18 shows the dura mater (dural sac) ending at the level of S2. Plates N160 or TG1-20 and N161 or TG1-18 label the filum terminale internum and externum (the externum is also called the coccygeal ligament seen in plate N160). Plate N169 or TG1-19 or TG1-21 shows the dura mater extending into the intervertebral foramen covering the dorsal root ganglion and spinal nerve. The dorsal root ganglion, spinal nerve, dorsal primary ramus, and ventral primary ramus are all seen in a close-up in the bottom picture of plate N169 or TG1-21. Plates N170, N180 or TG1-17, and N258 or TG1-21 also have these items labeled, but they present more of a "big picture" view, which might be helpful. The top picture in plate N169 or TG1-19 shows the dura mater being opened via mid-line incision like you will do in lab. The potential subdural space is unlabeled, but it is a potential space that can exist between the dura mater and the arachnoid layer. The subarachnoid space and the pia mater (covering the cord) are labeled in plate N169 or TG1-19. The denticulate ligament with its denticulation is seen in plate N169 or TG1-19. Plate N161 or TG1-18 shows the cervical and lumbar enlargements. The anterior (ventral) median fissure and posterior (dorsal) median sulcus are both labeled in plate N169 and can also be identified in plate N170, but are not labeled in this plate. The conus medullaris is shown in plates N160 or TG1-20 and N161 at the level of L2.

Step 5. Dissect out a spinal nerve laterally until it divides into primary rami. (Play movie)

Plate N170 or TG1-19 should give you an idea of how to find the dorsal root ganglion and spinal nerve. You will need to trace the dorsal primary ramus that you found earlier as it goes to the intervertebral foramen and remove more bone to expose the intervertebral foramen. Plate N169 or TG1-17 shows the dorsal and ventral rootlets (filaments) coming together to form dorsal and ventral roots. Plate N173 or TG1-21 shows the dura mater surrounding the dorsal root ganglion and spinal nerve in the intervertebral foramen. Plates N192 or TG1-17 and N258 or TG1-21 show the ventral primary rami as they travel below the lower surface of each rib, deep to the intercostal muscles. The cauda equina is shown in plates N160 or TG1-20 and N161. Plate N172 or TG1-21 shows the anterior spinal artery and posterior spinal arteries as you will see them in lab after cutting through the spinal cord. The vertebral artery can be seen at its origin in plates N138 and N136 or TG7-15 and TG1-09 as it branches off the subclavian artery and ascends within the transverse foramina of the cervical vertebrae. Before the vertebral arteries from each side unite as the basilar artery they each give off a posterior spinal artery (this artery may branch from the posterior inferior cerebellar artery as it branches from the vertebral artery, see plates N171 and N139 or TG7-56A and TG7-56B). Before uniting as the basilar artery, each vertebral artery also gives a contribution that unites to form the anterior spinal artery (plates N171 and N139 or TG7-56A and TG7-56B). The anterior and posterior spinal arteries are reinforced by segmental medullary arteries coming from the vertebral arteries, posterior intercostal arteries, and lateral sacral arteries (see plates N171 and N172 or TG1-19). Radicular arteries are shown in plate N172 or TG1-19 and TG1-21. The gray matter, white matter, ventral horn, lateral horn, and dorsal horn are all shown in plate N169. Plate N158 or TG1-11 (anterior vertebral segments picture) shows what the posterior longitudinal ligament and intervertebral disks will look like in the lab. The top picture in plate N158 or TG1-11 is an excellent overview of the ligaments of the spinal cord and their structural arrangement.