Prelab Images - Posterior Triangle of the Neck

Prelab Images - Posterior Triangle of the Neck

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 Atlas images listed below.
1. Review the bony landmarks. (Play movie)
Plates 6 and 8 show the foramen magnum, occipital condyles, hypoglossal canal, and jugular foramen (labeled as jugular fossa in plate 8). Plate 8 shows the external opening of the carotid canal. Plates 4 and 8 label the styloid process. Plate 186 shows the first rib, its grooves for the subclavian vein and artery and attachments of the scalene muscles to the first rib. The arrangement of rib one and the sternum is also seen in plate 186. Remove the clavicle if it is still present before beginning the dissection.
Step 2. Locate the accessory nerve and the roots of the cervical plexus. (Play movie)
Plate 28 shows the posterior triangle (bounded by the sternocleidomastoid, trapezius, and clavicle. The inferior belly of the omohyoid muscle subdivides the triangle into subclavian (inferior) and occipital (superior) triangles. Plate 71 shows the accessory nerve (CN XI) not far from where it exits the skull via the jugular foramen. Plates 32 and 72 (runs under the posterior lateral superficial cervical nodes in this plate, but is unlabeled) should help you find this nerve in the lab. Plate 127 also features CN XI. Plate 35 shows the superficial layer of deep cervical fascia where CN XI will be found deep to the sternocleidomastoid. Plates 32 and 129 show the relation of this nerve to the cutaneous nerves of the cervical plexus and the roots of the cervical plexus (ventral primary rami of C1-C4) can be seen in these plates.
Step 3. Follow the internal jugular vein to its termination noting its tributaries. (Play movie)
Plate 70 shows the internal jugular, superior, and middle thyroid veins. Plate 8 shows the jugular foramen where the internal jugular vein exits the skull. Plate 126 shows the glossopharyngeal, vagus, and accessory nerves leaving the skull through the same foramen. The subclavian vein unites with the internal jugular vein to form the brachiocephalic vein in plate 74. Plates 31 and 74 show the external jugular vein joining the subclavian. Plate 74 shows the transverse cervical and suprascapular veins (cut) coming from the external jugular vein. They should be near the arteries of the same name (plate 33). Identify the two veins and remove them. Plate 31 shows the anterior jugular vein traced and plate 256 shows the jugular venous arch (unlabeled) uniting across the midline. The anterior jugular vein forms the jugular venous arch and then terminates into the external jugular vein (256).
Step 4. Look for deep cervical lymph nodes and find the thoracic duct on the left. (Play movie)
Plate 72 shows the deep cervical lymph nodes (divided into superior and inferior groups by the omohyoid muscle) and the jugular trunk. Plates 239 and 266 show the thoracic duct receiving lymph from the jugular trunk and emptying into the junction of the subclavian and internal jugular veins (plate 239 shows the right jugular and subclavian trunks which are hard to find, but the right lymphatic duct is not shown). Also note the course the thoracic duct takes behind the esophagus in the thorax. Plate 74 shows the thoracic duct (unlabeled) near the anterior scalene muscle where you can find it in the lab. Plate 35 shows the prevertebral fascia. The anterior scalene muscle and phrenic nerve are shown in plates 34 and 36. The full course of the phrenic nerve can now be traced (plate 193). Plate 430 shows contributions to the phrenic nerve from the brachial plexus.
Step 5. Dissect the root of the neck to expose the subclavian arteries and their branches, the cervical sympathetic trunk and its ganglia, and the recurrent laryngeal nerve. (Play movie)
Plate 33 shows the brachiocephalic, common carotid, and subclavian arteries exposed throughout their course. The vagus nerve and phrenic nerve are shown in plate 33 and plates 130 and 131 show cardiac nerves (cervical sympathetic cardiac and cardiac branches from the vagus nerve). The prevertebral fascia and the location of the sympathetic trunk are shown in plate 35. This trunk is shown in plate 130 and the ansa subclavia and middle cervical ganglion are labeled. The recurrent laryngeal nerve is shown wrapping around the subcalvian artery on the right side and ascending in the tracheoesophageal groove in plates 130 and 232. Plate 136 has the superior, middle, and inferior (cervicothoracic or stellate) ganglion and the gray rami communicantes labeled. Plates 186 and 196 show the relationship of the first rib and the cupula of the lungs to the subclavian vessels. Plate 33 shows the junction of the subclavian and internal jugular veins cut, as you will need to do in the lab to identify the branches of the subclavian artery. Plates 33 and 136 show the vertebral artery and plate 130 shows its relation to the sympathetic trunk and ganglia. Plate 33 shows the thyrocervical trunk and the origin of the suprascapular and transverse cervical arteries. Plate 32 shows the transverse cervical and suprascapular arteries moving towards the back. Plate 427 shows the suprascapular artery supplying the shoulder and plate 177 shows the trapezius being supplied by the transverse cervical artery. Plate 135 shows the inferior thyroid artery and plates 75 and 76 show it coursing towards the thyroid gland. Plate 130 shows its relation to the sympathetic trunk and middle cervical ganglion. The internal thoracic artery is seen at its origin in plate 33 and being crossed by the phrenic nerve in plate 191. The dorsal scapular artery is shown at its origin near the anterior scalene muscle in plates 33 (top picture) and 427. Plate 32 shows the artery moving posteriorly through the brachial plexus (it travels fairly close to the transverse cervical and suprascapular arteries as all three make their way posteriorly). The dorsal scapular artery travels with the dorsal scapular nerve in the back to supply the rhomboids and levator scapulae muscles (plate 477, artery not pictured).
Step 6. Cut the anterior scalene muscle to expose the costocervical trunk, the roots of the brachial plexus and nerves arising from them. (Play movie)
Plate 33 shows the anterior scalene muscle. Cut through the attachment of this muscle to the first rib and reflect it superiorly to identify the costocervical trunk (seen in the bottom picture of plate 33). This trunk gives off the supreme intercostal artery and the deep cervical artery. The middle and posterior scalene muscles are identified in plate 30 and can also be seen in plate 33. Plate 430 organizes the brachial plexus and shows the origins of the suprascapular, dorsal scapular and long thoracic nerves. The suprascapular nerve can be seen in plates 429 and 477. The dorsal scapular and long thoracic nerves pierce the middle scalene muscle. Both nerves can be seen in plate 429. Plate 477 shows the dorsal scapular nerve and plate 185 shows the long thoracic nerve as well. Plate 33 shows the brachial plexus passing superior and posterior to the subclavian artery in the interscalene triangle (triangle bounded by anterior and middle scalene muscles and the first rib). Plate 186 shows the posterior scalene muscle inserting on the second rib, allowing it to elevate it during forced inspiration.