Unilateral Quadripartite Composition of Pectoral Major Muscle: Anatomical Description and Clinical Implications Composición Unilateral Cuadripartita del Músculo Pectoral Mayor: Descripción Anatómica e Implicancias Clínicas

DHURIA, R.; MEHTA, V.; LOH, H.; ARORA, J.; ROY, S. SURI, R. & RATH, G. Unilateral quadripartite composition of pectoral major muscle: Anatomical description and clinical implications. Int. J. Morphol., 27(4):1213-1216, 2009. SUMMARY: A unilateral anomalous disposition of the muscular slips of pectoralis major was observed in an adult male cadaver during routine gross anatomy teaching session. The pectoralis major muscle displayed unusual configuration and comprised of four parts delineated by three intramuscular clefts. Further, the sternocostal part was found to divide into two fasciculi. The origin and insertion of pectoralis major muscle was as usual and unremarkable. Interestingly, the innervation of the muscle was observed to bear an important variation. The clavicular and sternocostal slips of pectoralis major muscle received a direct branch from the lateral cord of brachial plexus in addition to its usual innervation from the lateral and medial pectoral nerves. The multiplicity of innervation of pectoralis major as encountered in the present study would presumably augment its suitability for its use in reconstructive procedures. An additional anomalous attachment of the pectoralis minor muscle was also observed emanating from the second rib, apart from the usual third, fourth and fifth ribs. These variants of the pectoral muscles may also have implications in biomechanical studies, as they may alter the kinematics.