A dissection is where the inner wall, or intima, gets a tear, and blood tracks into a false lumen in the vessel wall.

动脉内壁或者说内膜产生撕裂，血流随管壁的假腔中。

A small tear in the lining of the artery.

动脉内膜有个小裂口。

When progesterone reaches its lowest level, the spiral arteries collapse, and the functional layer dies off and is eliminated through menstruation, which marks the beginning of a new menstrual cycle.

当孕激素低水平，螺旋动脉破裂，子宫内膜功能层脱落，形成月经，也开启了一个新的月经周期。