(Return to Courseware Index) Name the four walls of the axilla and the muscles they contain. Identify the interscalene triangle in the posterior triangle of the neck and observe how the roots of the brachial plexus and the subclavian artery pass through it. Identify the pectoralis major and pectoralis minor, their nerve supply and blood supply. Learn the regions and branches of the axillary artery. Remember that the first part has one branch, the second part has two branches, and the third part has three branches. Learn the two anastomoses between the subclavian artery and the axillary artery. Observe and identify the divisions, cords and branches of the brachial plexus. Learn how the arm is divided into two compartments that share common functions, nerve and blood supplies. Learn the bony landmarks on the distal humerus and proximal ulna and radius. Identify the boundaries and contents of the cubital fossa. Learn which bones the muscles of the arm attach to. You do not need to know specific origins and insertions. Hone your scissor technique by dissecting the left axilla to match the right axillary dissection.
The posterior triangle of the neck has already been partially dissected so that you can see the roots of the brachial plexus and the subclavian artery that provide innervation and blood, respectively to the upper limb. The borders of the posterior triangle are anteriorly – posterior border of the sternocleidomastoid muscle, posteriorly – the anterior border of the trapezius muscle and inferiorly – the middle third of the clavicle. P. 19: As you can see, the axilla has been fully dissected on the right side. One of your goals today will be to match the dissection on the left side. Before you do so, spend 15 - 20 minutes examining the axillary dissection on the right side identifying nerves and arteries with the help of the dissector and atlas P. 20: Once you have spent 15-20 minutes looking at the predissected right axilla, start your own axillary dissection on the left side. Each lab partner should dissect the axilla for at least 15 minutes to really hone your scissor technique. Instructors will circulate to give you pointers and answer questions - they will not do the dissection for you. REMEMBER THIS IS YOUR OPPORTUNITY TO PRACTICE DISSECTING WITHOUT WORRYING ABOUT LOSING OR DESTROYING STRUCTURES BECAUSE THE RIGHT SIDE IS ALREADY FULLY DISSECTED AND CAN BE STUDIED. P.20 Begin the dissection by cleaning the borders of the pectoralis major muscle and identifying the cephalic vein that runs in the deltopectoral triangle. After you can clearly see the borders of the pectoralis major muscle, insinuate your fingers beneath the pectoralis major muscle and then sweep your fingers towards the axilla. Observe the way the pectoralis major was cut on the right and mimic it using scissors and keeping directly next to the clavicle when you cut across the clavicular head. Reflect the pectoralis major muscle laterally and then cut across the pectoralis minor muscle and reflect it, using your newly learned scissor technique to release the pectoralis minor muscle from the chest wall. Be careful not to disturb the lateral thoracic artery and vein that run along the thoracic wall. P. 22: Proceed with the arm and cubital fossa dissection on the RIGHT arm. P. 24: Be sure not to cut any muscles until all your lab partners have gotten a chance to see them intact. When you do transect the muscles do so at different levels so that you can correctly match up the two ends of each muscle. The completeness of your axillary dissection on the left side will be assessed at the end of next week. Narrowing can occur due to an accessory (extra) rib, or additional muscle slips. The narrowing may compress the subclavian artery and/or roots of the brachial plexus, which can restrict blood supply and affect innervation to the upper limb. 3.Will the collateral circulation provided by the anastomoses around the elbow joint save a patient’s arm during an acute occlusion of the brachial artery – ie suddenly? How about during a gradual occlusion?
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