The axilla has many things that traverse it. It provides a means of nerves, vessels to enter the arm. It contains the axillary artery and its branches, axillary vein and its tributaries, part of the brachial plexus and axillary lymph nodes. The axilla also contains the short and long head of the biceps brachii, the coracobrachialis muscle. The tail of the breast feeds into the axillary region, and all of these structures are embedded in fat tissue (adipose).

Major Points: Axillary artery  Axillary Vein  Brachial Plexus  Axillary Lymph Nodes  short and long heads of biceps brachii  coracobrachialis  tail of the breast  adipose tissue

Possible Question: List the contents of the axilla. What are the anterior borders of the axilla?

Course of the Axillary Artery

The axillary artery is the continuation of the subclavian artery after the first rib. Near the apex of the axilla, it travels behind the axillary vein, but then comes to lie lateral to it. The axillary artery and parts of the brachial plexus are surrounded by an axillary sheath. The axillary artery is split into three parts, conventionally named by the division of the pectoralis minor. Each division gives off corresponding number of branches. Distal to the lower border of teres major, the axillary artery continues as the brachial artery.

An arterial anastomosis exists at the scapula region. This anastomosis is contributed by branches of the subclavian and axillary arteries. It involves communications between the circumflex scapular artery, dorsal scapular artery and suprascapular artery.

Major Points: Continuation of the subclavian artery after the first rib  posterior and lateral relations to the axillary vein  axillary sheath  conventional divisions and associated branches  continues as brachial artery at the lower border of teres major  arterial anastomosis at scapula region  arteries contributing to this anastomosis  dorsal scapular, circumflex scapular and suprascapular artery.

Possible Question: Describe the arterial anastomosis formed at the scapula region.

Possible (T/F) Question: The axillary artery is the continuation of the subclavian artery after the lower end of the teres major muscle (Answer: False, it is continuation of the subclavian artery after the first rib).

Axillary Vein

The basilic vein (medial) and the venae comitantes of the brachial artery join to form the axillary vein, at the medial aspect of the arm just above the inferior border of teres major. The vein ascends medially to the axillary artery but then comes to lie anterior to this artery before continuing as the subclavian vein after the lateral edge of the first rib. The major tributary of this vein is the cephalic vein which ascends in the groove between the deltoid and pectoralis major muscles. It pierces the fascia just below the clavicle to drain into the axillary vein.

Possible (T/F) Question: The basilic vein joins with the venae comitantes of the brachial artery to form the subclavian vein. (Answer: False  first it forms the axillary vein, then the subclavian vein)

Possible (T/F) Question: The basilic vein joins with the venae comitantes of the brachial artery to form the axillary vein just above the inferior border of the teres major muscle. Then it continues posteriorly to the axillary artery and after the lateral edge of the first rib it continues as the subclavian artery (Answer: False, it first travels medially and then anterior to the corresponding artery).

Possible (T/F) Question: The cephalic vein is the principal tributary of the axillary vein and comes to pierce the fascia beneath the clavicle to drain into the axillary vein. (Answer: True).

Possible (T/F) Question: The cephalic, basilic and venae comitantes of the upper limb are the equivalent of the long saphenous, venae comitantes and short saphenous veins of the lower limb. (Answer: True).

Axillary Lymph Nodes

There are a number of axillary nodes located near the root of the upper limb. Anteriorly, we have the pectoral nodes which drain the anterior and lateral aspects of the body wall including the breast. Posteriorly, there is the subscapular nodes which drain the dorsal aspect of the body wall. Laterally, there are two groups of nodes namely: brachial and humeral. These receive lymph mainly from the upper limb. Within the axilla lymphatic vessels drain centrally and more proximally to the apical nodes.

Through the upper limb there are also other nodes present. The Cubital nodes and the infraclavicular.

Major Points: Anterior  pectoral nodes, drain the anterior and lateral aspects of the body wall  Posterior  subscapular nodes, drain the dorsal aspect of the body wall  Lateral  brachial and humeral nodes which drain mostly the upper limb  Within the axilla, lymphatic vessels drain into the central node and then more proximally into the apical nodes.  also other nodes present, Cubital and infraclavicular nodes.

Brachial Plexus

You should be able to draw the brachial plexus. This can be asked in the gross anatomy theory paper. I think it will be one of the big essay questions.

Extends from C5-T1 spinal roots.

Category: Anatomy Notes