Complex sentence: Its only direct territorial afferents are those which accompany the cephalic vein and one which drains the upper peripheral part of the mamma, but it receives the efferents of all the other axillary glands.
Split into simpler sentences: Its only direct territorial afferents are those that accompany the cephalic vein, and one that drains the upper peripheral part of the mamma. However, it receives the efferents of all the other axillary glands.