Identify the deep structures of the posterior triangle of the neck.

1. Identify the inferior belly of the omohyoid muscle. (G 8.10;N 28;Gl 39.31)
2. Identify the axillary and trace it proximally until it passes posterior to the anterior scalene muscle. (G 8.5F;N 29 and 417;Gl 39.31) At this point the vessel is the subclavian artery. Identify the phrenic nerve and transverse cervical and suprascapular arteries anterior to the anterior scalene muscle.
Important Relationships
• The subclavian artery passes directly posterior to the anterior scalene muscle.
• The phrenic nerve and subclavian vein pass directly anterior to the anterior scalene muscle.
• The suprascapular and transverse cervical arteries typically pass directly anterior to the anterior scalene muscle.
3. Identify the trunks of the brachial plexus where they emerge posterior to the anterior scalene muscle. Identify the suprascapular nerve arising from the upper trunk. Trace the suprascapular nerve and artery to the superior transverse scapular ligament (Shoulder and Posterior Arm observation).
   Important Relationships

   • The brachial plexus (roots) are positioned directly anterior to the middle scalene and directly posterior to the anterior scalene muscles.