The upper fascicle emerged from the anterior wall of the thorax as a thin muscular extension of the pectoral fascia and the anterior sheet of the clavipectoral fascia
. From its origin, this fascicle was directed to the axillary fossa, joining in this trajectory with the middle fascicle emerging from the latissimus dorsi muscle, although clearly separated from it.
It continues along the lateral border of the biceps muscle to the deltopectoral groove and perforates the clavipectoral fascia to drain into the axillary vein .
Later studies, however, found that the cephalic vein courses in the upper arm lateral to biceps, to the deltopectoral groove, and perforates the clavipectoral fascia in the infraclavicular fossa to drain into the axillary vein .
The pectoral fascia was dissected and the pectoralis major was cut at its humeral insertion, permitting identification of the clavipectoral fascia immediately above the pectoralis minor muscle.
Furthermore, there was no alteration in the relationship of the fascicles with adjacent vascular structures, or in their deep location to the clavipectoral fascia and pectoralis minor.
Pectoralis major and minor muscles were reflected and the clavipectoral fascia
removed together with the axillary sheath which surrounded the axillary vessels and the brachial plexus.