They say it takes some training. And there can be risks, like running when your feet are too cold to feel if you get injured.

VOA: special.2010.02.03

Some form what are called megakaryocytes which become platelets, which are responsible for clotting, for forming a barrier if your circulatory system gets injured so you don't bleed.

还有一些类型的细胞称为巨核细胞,生成有凝血作用的血小板,在你的循环系统受损时形成止血屏障

耶鲁公开课 - 生物医学工程探索课程节选