Blood Supply and Innervation – Breast

00:01 The arterial supply to the breast is quite numerous. We'll have branches from the axillary artery. We'll have branches from the internal thoracic artery and then we'll have contributions from the 2nd through the 4th intercostal arteries. Not all these vessels are shown in this particular illustration, but let's take a moment to highlight those for you.

00:24 Here, we have our axillary artery. Axillary artery is divided into three parts. Part 1 lies to the medial aspect of your pec minor. Part 2 is lying deep to the pec minor and then the third part will continue lateral to your pec minor. There is a slender branch from the first part shown here. This is the superior thoracic artery and you can see some branches supplying the breast. Another branch that is shown here is this one coming from the second part. This is your lateral thoracic artery. We see the internal thoracic artery, in this case, the right one, traveling along the right lateral margin of the sternum and you can see branches supplying the breast. And then intercostal spaces that lie deep to the breast and the pectoral muscles will send penetrating branches into the deep tissue of the breast. Venous drainage is primarily through these three veins, the internal thoracic vein, the lateral thoracic vein and then the intercostal veins. The internal thoracic vein is shown here and it accompanies the internal thoracic artery. And so, you can see some venous blood draining toward the internal thoracic vein.

02:01 We also have our lateral thoracic vein accompanying the lateral thoracic artery and similarly, you can see some of the delicate branches that are draining blood from the lateral margins of the breast into the lateral thoracic vein. On the following slide about lymphatic drainage, there is a key take-home message. That message is, 75% of the lymph draining from the breast will drain to the axillary lymph nodes. Those axillary lymph nodes are located right in through here and they are clinically said to reside in three levels.

02:47 Level 1 axillary nodes are shown in through here. They lie lateral to the pectoralis minor.

02:55 Level 2 lymph nodes, clinically, are said to reside underneath the pec minor. And then level 3 axillary lymph nodes lie medial to the pectoralis minor. 75% of the lymph is directed into these axillary nodes. Majority of the lymph that isn't directed into the axillary nodes will drain medially into the lymph nodes that are associated with the internal thoracic vasculature. And you see some lymph nodes here, for example. One's right there, one's right here. These are parasternal lymph nodes, also known as internal mammary lymph nodes and then some lymph from the skin of the breast will drain into the abdominal nodes and can also drain over into the opposite breast.

03:56 Innervation to the breast is supplied by sensory and sympathetic fibers that travel or are conveyed in intercostal nerves that travel in intercostal spaces 2 through 6. In this particular illustration, we have our spinal cord, we have a typical spinal nerve and then we have our typical spinal nerve branching into an anterior ramus. And when these anterior rami are associated within the intercostal spaces, these become intercostal nerves. In addition, you have a sympathetic structure and this is a sympathetic trunk. And there are delicate connections from the sympathetic trunk into your spinal nerves and their branching pattern. And this is the way that sympathetic fibers will get conveyed into these intercostal nerves.