Brachial Plexus, Arm, Cubital Fossa

Brachial plexus (begins superior to the clavicle → distal part of axilla). Only the infraclavicular portion of the brachial plexus will be followed at this time, the supraclavicular portion should be identified when studying the neck.
Roots→ Trunks→ Divisions→ Cords→ Terminal Branches.

The best way to find these nerves is to work from the bottom up. Find the coracobrachialis muscle. The musculocutaneous nerve innervates this muscle → follow the musculocutaneous nerve superiorly → lateral cord → follow medially where it gives rise to the lateral root of the median nerve → follow distally to find the median nerve → follow proximally, and then medially to the medial root of median nerve → follow distally to the ulnar nerve or proximally to the medial cord. *Notice that the three terminal branches (musculocutaneous, median, and ulnar nerves) form the letter “M” anteriorly to the third part of the axillary artery).
Find the medial and lateral pectoral nerves on the pectoral muscles and follow them to their origins on the lateral and medial cords. Identify two branches on the inferior edge of the medial cord → medial cutaneous nerve of the forearm and medial cutaneous nerve of the arm.
Posteriorly to the superior portion of the axillary artery, lateral cord, and medial cord the posterior cord can be found. Follow the posterior cord distally → 3 subscapular nerves (upper, middle, and lower) which are the most proximal → distally and the posterior cord ends when it branches to become the axillary nerve and radial nerve.

The upper subscapular nerve innervates the subscapularis muscle. The middle subscapular nerve (aka thoracodorsal nerve) innervates the latissimus dorsi muscle. The lower scapular nerve innervates the subscapularis and teres major muscles.
The axillary nerv runs posteriorly to the humerus with the posterior circumflex artery.
The radial nerve leaves the axilla posteriorly to the humerus.

Follow the musculocutaneous nerve (which innervates the 3 muscles of the anterior compartment) from the coracobrachialis muscle → penetrates between the biceps brachii muscle and brachialis muscle → gives off muscular branches (don’t follow these) → keep following the nerve and it become the lateral cutaneous nerve of the forearm → follow to cubital fossa where it emerges at the lateral side of the biceps brachii tendon. *Note the lateral cutaneous nerve of the forearm runs near the cephalic vein.
The medial cutaneous nerve of the forearm can be found at the level of the elbow by the basilic vein and can be followed proximally to the brachial plexus in the axilla.
The median nerve runs from the axilla/brachial plexus → cubital fossa→ forearm.
Medial cord → ulnar nerve → medial epicondyle of humerus → forearm.
Axillary artery at brachial plexus → follow and it becomes the brachial artery at the level of the inferior border the the teres major muscle→ brachial artery ends at the level of the elbow → ulnar artery and radial artery. *The brachial artery runs with the median nerve.

Brachial artery has 3 named branches in the arm, and several unnamed branches.

Deep artery of the arm runs posteriorly on the humerus with the radial nerve in the radial groove (seen if the posterior arm is dissected).
Superior ulnar collateral artery branches from the brachial artery near the middle of the arm and courses distally with the ulnar nerve → then posteriorly to the medial epicondyle of the humerus.
Inferior ulnar collateral artery branches from the brachial artery above the medial epicondyle and runs anteriorly between the brachialis muscle and the pronator teres muscle.
Axillary artery → brachial artery → gives off deep artery of arm, superior ulnar collateral artery, and inferior ulnar collateral artery (listed proximally → distally).

Cephalic vein, basilic vein, median vein, brachial artery, and median nerve. Follow each down to the fossa from instructions given previously.

Inferiorly to teres major muscle, there is an opening between the long head of the triceps brachii muscle and lateral head of triceps brachii. The radial nerve and deep artery of the arm can be found here.
Follow the radial nerve distally (on the flexor side) to the elbow where it is accompanied by the radial recurrent artery.

Kiwi Med