Session 17: Axilla and brachial plexus Flashcards
Why is the axilla important clinically?
As it is a common site for malignancy
Where does the brachial plexus arise from
Cervical nerve roots 5/6/7, C8 and T1
How do they arise
Arise through the intervertebral foramina. Run inferiorly and laterally through the axilla
Role of the phrenic nerve
Motor and sensory supply to the diaphragm
How does the brachial plexus form?
5 nerve roots run inferiorly + laterally through the axilla. They combine/divide/combine/divide to form the B.P. Results in mixed peripheral nerves
What muscle is in front of the brachial plexus?
The scalene anterior muscle
What two muscles do the roots of the brachial plexus
The scalene anterior and the scalenus medius
What are the nerves of the brachial plexus surrounded by?
Loose areolar tissue (remember the shoulder etc has to move so the brachial plexus needs to be flexible)
Where is the lower part of the brachial plexus?
At the anterior axillary fold (this is the lowest border of the pectoralis major)
What artery enters the axilla?
The subclavian artery
What are the three main cords formed?
Posterior/lateral/medial
What does the posterior trunk give rise to?
The radial nerve and axillary nerve (+ 3 smaller nerves: the upper and lower subscapular nerves and the thoracodorsal nerve)
What does the lateral cord give rise to?
It divides into a musculo-cutaneous + a lateral part which becomes the median nerve
What does the medial cord give rise to?
Splits into two: the ulna nerve and the medial part of the median nerve
‘M’ shape: what does it go from
Goes from lateral to medial to musculocutaneous to median nerve to ulna nerve
Anterior arm: what is the groove between the pectoralis major and deltoid muscle called?
The deltopectoral groove
What vein runs between the posterior and anterior compartments of the arm?
The cephalic vein
What does the cephalic vein join to at the antecubital fossa?
The basilic vein. This then runs to join an artery to form the brachial vein
When the brachial vein passes into the axilla what does it become?
The axillary vein (then the subclavian vein/brachiocephalic vein/superior V.C to the heart)
What is the name of the nerve that supplies the anterior compartment of the arm?
The musculocutaneous nerve
What muscles does the musculocutaneous nerve supply?
Biceps, brachialis and coracobrachialis muscles
What are the two origins of the biceps muscle
- ) Long head of biceps runs as a tendon. It is deep to pectoralis in the bicipital groove. Origin is in the superior aspect of the glenoid fossa
- ) Short head of biceps has it origin on the coracoid
Origin of the triceps muscle
Attached to the inferior aspect of the glenoid fossa
What is the other muscle that also has its origin on the coracoid?
The coracobrachialis. Is a shorter/smaller muscle. Inserts onto the humerus. Lies beneath short head of biceps
Where is the antecubital fossa?
Lies immediately in front of the elbow
Why is it an important area?
Main site for blood sampling
What vein is located here?
The cephalic vein: lies in front of the biceps aponeurosis
What is the antecubital fossa formed by?
By brachorialis/ the brachoradialis muscle
