external blood的用法和樣例：
例句
- Currently, EPCs have been identified in adult peripheral blood, bone marrow, and human umbilical cord blood.
目前，內皮祖細胞已被證實存在於成年人外周血，骨髓和人臍帶血中。 - They are infrequent in a normal peripheral blood smear, and their significance is uncertain.
它們在正常的外周血塗片中是很少見的，而且它們的意義還不確定。
