The urinary bladder is a hollow, muscular and distendible or elastic organ that sits on the pelvic floor.

膀胱是一个位于盆底的空腔、肌肉发达、可扩张或有弹性的器官。

Today, doctors use cardiac catheterization methods to close certain kinds of holes in the heart or to place expandable valves.

，医生使用导检查方法来封中的某些类型的孔洞或放置可扩张的瓣膜。

We also needed to know the size of the mouth, because they have these enormous expandable pouches that they fill with water and prey.

马修：我们也需要知道它们嘴巴的大小，因为它们有着巨大的可扩张囊袋，用来装水和猎物。