the outer covering

Component structure of the outer covering and flight surfaces of all modern birds.

现代鸟类体表和翼面覆盖的结构。

The outer covering of the egg is waterproofed to prevent the embryo from drying out.

鸡蛋的外壳是不透水的，防止胚胎失水。

This can lead to something called an epidural haematoma, where blood builds up between the outer covering of the brain and the skull, with consequent pressure on the brain itself.

这种情况会产生硬膜血肿，也就是血液充满大脑外膜和颅腔，压迫大脑本身。