Session 17: Axilla and brachial plexus

Question 1

Why is the axilla important clinically?

Answer 1

As it is a common site for malignancy

Question 2

Where does the brachial plexus arise from

Answer 2

Cervical nerve roots 5/6/7, C8 and T1

Question 3

How do they arise

Answer 3

Arise through the intervertebral foramina. Run inferiorly and laterally through the axilla

Question 4

Role of the phrenic nerve

Answer 4

Motor and sensory supply to the diaphragm

Question 5

How does the brachial plexus form?

Answer 5

5 nerve roots run inferiorly + laterally through the axilla. They combine/divide/combine/divide to form the B.P. Results in mixed peripheral nerves

Question 6

What muscle is in front of the brachial plexus?

Answer 6

The scalene anterior muscle

Question 7

What two muscles do the roots of the brachial plexus

Answer 7

The scalene anterior and the scalenus medius

Question 8

What are the nerves of the brachial plexus surrounded by?

Answer 8

Loose areolar tissue (remember the shoulder etc has to move so the brachial plexus needs to be flexible)

Question 9

Where is the lower part of the brachial plexus?

Answer 9

At the anterior axillary fold (this is the lowest border of the pectoralis major)

Question 10

What artery enters the axilla?

Answer 10

The subclavian artery

Question 11

What are the three main cords formed?

Answer 11

Posterior/lateral/medial

Question 12

What does the posterior trunk give rise to?

Answer 12

The radial nerve and axillary nerve (+ 3 smaller nerves: the upper and lower subscapular nerves and the thoracodorsal nerve)

Question 13

What does the lateral cord give rise to?

Answer 13

It divides into a musculo-cutaneous + a lateral part which becomes the median nerve

Question 14

What does the medial cord give rise to?

Answer 14

Splits into two: the ulna nerve and the medial part of the median nerve

Question 15

‘M’ shape: what does it go from

Answer 15

Goes from lateral to medial to musculocutaneous to median nerve to ulna nerve

Question 16

Anterior arm: what is the groove between the pectoralis major and deltoid muscle called?

Answer 16

The deltopectoral groove

Question 17

What vein runs between the posterior and anterior compartments of the arm?

Answer 17

The cephalic vein

Question 18

What does the cephalic vein join to at the antecubital fossa?

Answer 18

The basilic vein. This then runs to join an artery to form the brachial vein

Question 19

When the brachial vein passes into the axilla what does it become?

Answer 19

The axillary vein (then the subclavian vein/brachiocephalic vein/superior V.C to the heart)

Question 20

What is the name of the nerve that supplies the anterior compartment of the arm?

Answer 20

The musculocutaneous nerve

Question 21

What muscles does the musculocutaneous nerve supply?

Answer 21

Biceps, brachialis and coracobrachialis muscles

Question 22

What are the two origins of the biceps muscle

Answer 22

1. ) 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
2. ) Short head of biceps has it origin on the coracoid

Question 23

Origin of the triceps muscle

Answer 23

Attached to the inferior aspect of the glenoid fossa

Question 24

What is the other muscle that also has its origin on the coracoid?

Answer 24

The coracobrachialis. Is a shorter/smaller muscle. Inserts onto the humerus. Lies beneath short head of biceps

Question 25

Where is the antecubital fossa?

Answer 25

Lies immediately in front of the elbow

Question 26

Why is it an important area?

Answer 26

Main site for blood sampling

Question 27

What vein is located here?

Answer 27

The cephalic vein: lies in front of the biceps aponeurosis

Question 28

What is the antecubital fossa formed by?

Answer 28

By brachorialis/ the brachoradialis muscle