When Going along with the fifth metacarpal bone head, the descending branch or little finger artery ulnaris sent off the降支或小指动脉尺侧支循第 掌骨头尺侧走行时发 ～ 支、外径 0 . ～ 0 .7mm骨膜支 ,分布于第 掌骨背内面骨膜。