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 or LWW Atlas images listed below.

1. Review the bony landmarks. (Play movie)

Plates N6 or TG7-08 and N8 or TG7-06 show the foramen magnum, occipital condyles, hypoglossal canal, jugular foramen, and the external opening of the carotid canal. Plates N4 or TG7-32 and N8 or TG7-06 label the styloid process. Plate N186 or TG7-15A 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 N186 or TG7-15B. 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 N28 or TG7-12, TG7-16 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 (TG7-02A, TG7-02B). Plate N71 or TG7-18 shows the accessory nerve (CN XI) not far from where it exits the skull via the jugular foramen. Plates N32 or TG7-17 and TG7-18 and N72 (runs under the posterior lateral superficial cervical nodes in this plate, but is unlabeled) should help you find this nerve in the lab. Plate N127 or TG7-93 also features CN XI. Plate N35 or TG7-10 shows the superficial layer of deep cervical fascia where CN XI will be found deep to the sternocleidomastoid. Plates N32 and N129 or TG7-16, TG7-17 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 N70 or TG7-13 shows the internal jugular, superior, and middle thyroid veins. Plate N8 or TG7-06 shows the jugular foramen where the internal jugular vein exits the skull. Plate N126 or TG7-51, TG7-75 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 N74 or TG7-73. Plates N31 or TG7-13 and N74 or TG7-73 show the external jugular vein joining the subclavian. Plate N74 or TG7-16 shows the transverse cervical and suprascapular veins (cut) draining to the external jugular vein. They should be near the arteries of the same name (plate N33 or TG7-15). Identify the two veins and remove them. Plate N31 or TG7-73 shows the anterior jugular vein traced and plate N256 or TG7-11 shows the jugular venous arch uniting across the midline. The anterior jugular vein forms the jugular venous arch and then terminates into the external jugular vein (N256 or TG7-73).

Step 4. Look for deep cervical lymph nodes and find the thoracic duct on the left. (Play movie)

Plate N72 or TG7-74 shows the deep cervical lymph nodes (divided into superior and inferior groups by the omohyoid muscle) and the jugular trunk. Plates N239 or TG4-44 and N266 or TG5-37 show the thoracic duct receiving lymph from the jugular trunk and emptying into the junction of the subclavian and internal jugular veins (plate N239 or TG4-44 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 N74 or TG7-14 shows the thoracic duct (unlabeled) near the anterior scalene muscle where you can find it in the lab. Plate N35 or TG7-10 shows the prevertebral fascia. The anterior scalene muscle and phrenic nerve are shown in plates N34 or TG7-15 and N36 or TG7-17 and TG7-18. The full course of the phrenic nerve can now be traced (plate N193 or TG4-18). Plate N430 or TG7-14 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 N33 or TG7-15 shows the brachiocephalic, common carotid, and subclavian arteries exposed throughout their course. The vagus nerve and phrenic nerve are shown in plate N33 or TG7-14 and plates N130 or TG7-95 and N131 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 N35 or TG7-10. This trunk is shown in plate N130 or TG7-15 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 N130 or TG7-19 and N232 or TG7-14. Plate N136 or TG7-15 has the superior, middle, and inferior (cervicothoracic or stellate) ganglion and the gray rami communicantes labeled. Plates N186 or TG4-20 and N196 or TG4-15 show the relationship of the first rib and the cupula of the lungs to the subclavian vessels. Plate N33 or TG7-14 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 N33 and N136 or TG7-15B show the vertebral artery and plate N130 or TG7-15A shows its relation to the sympathetic trunk and ganglia. Plate N33 or TG7-15B shows the thyrocervical trunk and the origin of the suprascapular and transverse cervical arteries. Plate N32 or TG7-17 and TG7-14 shows the transverse cervical and suprascapular arteries moving towards the back. Plate N427 or TG2-15 shows the suprascapular artery supplying the shoulder and plate N177 or TG1-13 shows the trapezius being supplied by the transverse cervical artery. Plate N136 or TG7-15 shows the inferior thyroid artery and plates N75 or TG7-14 and N76 show it coursing towards the thyroid gland. Plate N130 or TG7-15 shows its relation to the sympathetic trunk and middle cervical ganglion. The internal thoracic artery is seen at its origin in plate N33 or TG4-09 and being crossed by the phrenic nerve in plate N191 or TG7-15B. The dorsal scapular artery is shown at its origin near the anterior scalene muscle in plates N33 or TG7-15 and N427 or TG2-15. Plate N32 or TG7-15B and TG7-15A 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 N477 or TG2-09).

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 N33 or TG7-15A 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 N33 or TG7-15B). This trunk gives off the supreme intercostal artery and the deep cervical artery. The middle and posterior scalene muscles are identified in plate N30 or TG7-15 and can also be seen in plate N33 or TG7-15. Plate N430 or TG2-13 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 N429 or TG2-14 and N477 or TG2-13. The dorsal scapular and long thoracic nerves pierce the middle scalene muscle. Both nerves can be seen in plate N429 or TG2-13. Plate N477, N185 or TG2-13 shows the dorsal scapular nerve and long thoracic nerve. Plate N33 or TG7-15 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 N186 or TG7-15 shows the posterior scalene muscle inserting on the second rib, allowing it to elevate it during forced inspiration.