Axillary artery

The Axillary artery is the continuation of the subclavian a., starting from the lateral border of the first rib and continuing to the inferior border of the teres major muscle. As the axillary a. passes distal to the teres major muscle, its name changes to the brachial artery.

Note in the picture above the 3-D ‘tube’ nature of the brachial plexus, organized around the axillary. As such, the axillary a. lies between the medial and lateral cords of the brachial plexus (and its branches that run parallel, such as the musculocutaneous and ulnar nn.), as well as anterior to the posterior cord (and its parallel branches, the axillary and radial nn.) and posterior to the median n.

The axillary a. is commonly divided into three sections:

The first part lies between its beginning (lateral border of the first rib) and the medial border of pectoralis minor muscle.

The second part is posterior to the pectoralis minor muscle (and is therefore defined by the medial and lateral borders of that muscle).

The third part lies between the lateral border of the pectoralis minor muscle and inferior border of teres major muscle (the terminus of the axillary a, after which it continues as the brachial a.).

Picture from http://home.comcast.net/~WNOR/lesson3axillaryart&vein.htm.

The three defined parts of the axillary a. are useful in remembering the major branches of the artery: the first part has one major branch, the second part has two major branches, and the third part has three major branches.

1^st part – Superior thoracic a.

2^nd part – Thoracoacromial trunk (and its branches) and lateral thoracic a.

3^rd part – Ant. & post. humeral circumflex aa. and the subscapular a. (and its branches).

Picture from http://ect.downstate.edu/courseware/haonline/figs/105/050401.htm.

Or a less busy illustration (from Grant’s):