Ansa pectoralis

There is a communicating branch that loops from the (deep branch of the) lateral pectoral nerve to the medial pectoral nerve, called Ansa pectoralis [from Latin: ansa = a handle.]. Ansa pectoralis passes anterior to axillary artery and vein, usually distal to the thoracoacromial trunk. This communication consists of fibers from the lateral cord of the brachial plexus, and is assumed to provide some degree of redundant innervation to the pectoralis minor m. This would explain the continued (if possibly weaker) functioning of pectoralis minor even after transection of the medial pectoral nerve (between its origination and the insertion of ansa pectoralis). Obviously, electrophysiologic studies could prove quite useful in evaluating the functional significance of the ansa pectoralis. In addition, histological sections could aid in determining the types of nerve fibers contained within the ansa pectoralis (Loukas et al, 2007).

(AP = ansa pectoralis; TAA = thoracoacromial a.)

Pictures from: Loukas M, Louis Jr R, Fitzsimmons J, and Colborn G. 2007. The surgical anatomy of the ansa pectoralis. Clin Anat 19(8):685:693.