Additionally, spiral arteries emerge to nourish the growing functional endometrium.

此外，螺旋动脉出现以供养生长中的子宫内膜功能层。

If fertilization doesn't occur, the spiral arteries collapse, and the superficial layers of the endometrium die.

如果卵子没有受精，螺旋动脉将会收缩，子宫内膜的表层也会因此凋亡。

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.

当孕激素达到最低水平，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。

Normally, during pregnancy, the spiral arteries dilate to 5-10 times their normal size and develop into large uteroplacental arteries capable of delivering large quantities of blood to the developing fetus.

正常妊娠中，子宫螺旋动脉可以扩张至原先直径的5-10倍，并发育成粗大的子宫胎盘动脉，从而向发育中的胎儿输送大量血液。

During the follicular phase of the menstrual cycle, the endometrium thickens in case fertilization occurs, during the luteal phase, spiral arteries emerge to bring more nutrients to support the thick endometrium.

在月经周期中的卵泡期，子宫内膜会变厚，有助于受精；黄体期，螺旋动脉产生可以为增厚的子宫内膜提供更多养分。