**4. Innervation, lymphatics and blood supply**

Sensory innervation is derived from cervical plexus, anteromedial and anterolateral intercostal nerve branches from the 3rd, 4th, 5th and 6th intercostal nerves as well as branches from the 2nd intercostal nerve. Of particular concern for surgeons is the innervation of the nipple, which has crossover innervation from 3rd to 5th nerves medial and laterally, but primarily derived from the 4th lateral cutaneous branch. This branch tends to run along the fascia of pectorals major before emerging to innervate the nipple from its posterior surface.

Most of the lymphatic drainage of the breast flows into the axilla through the external mammary nodal group, however additional drainage occurs through the medial, transpectoral and postdoctoral routes as well.

 The internal mammary artery supplies the majority (approximately 60%) of the blood supply to the breast. Its branches pass through the intercostal muscles, from the 2nd through 5th ribs immediately lateral to the parasternal border. These coalesce once in the breast with additional contributions from lateral thoracic branches, pectoral branches from in internal thoracic artery and branches from the posterior intercostal arteries. Venous outflow occurs via an anastomotic plexus in the subcutaneous tissue immediately beneath and around the NAC. This plexus then drains peripherally via large subcutaneous veins that empty into intercostal and axillary veins as well as internal thoracic veins. Importantly, the largest and most reliable venous routes reside in the superomedial and inferior pedicles. Congestion of these routes and the subareolar plexus are usually the primary causes of NAC ischemia and necrosis in mastopexy procedures [1].

#### **Figure 4.**

*The figure demonstrates the two major sources of blood supply to the Superomedial-Central (SMC) pedicle. The medial source from branches of the internal mammary artery and central component from the pectoral perforators. The 2nd medial perforator supplies the most superomedial area of the SMC pedicle. Maintaining all these sources during dissection produces a robustly vascularized pedicle.* 

#### **Figure 5.**

*The central component vascularization of the SMC pedicle is helpful when implant placement is submuscular. Submammary dissection transects most of the central perforators leaving only the medial perforators for blood supply to the NAC. The incision through muscle must be made just inferior to the central blood supply. Incision at the lateral pectoralis border can be used as well but does not work as well for obtaining a total muscular coverage of an implant.* 
