医学英语翻译

The outer layers of the cyst wall comprise a number of blood vessels.the progressive increase in cyst volume through secretion of the biliary epithelium increases interacystic pressure which probably induces necrosis in internal layers, hence exposing blood vessels to alterations in their outer wall and, consequently, intracystic bleeding.

这是一篇英文文献，其中exposing blood vessels to alterations in their outer wall 这句话百思不得其解，恳请 老师们给一些指点！  谢谢