membranous structure that functions as the circulatory system in mammal embryos until the heart becomes functional
同义词：vitelline sac??/??umbilical vesicle??/??vesicula umbilicus
membranous structure enclosing the yolk of eggs in birds reptiles marsupials and some fishes; circulates nutrients to the developing embryo
英汉双解词典包含3185865条英汉词条，基本涵盖了全部常用单词的翻译及用法，是英语学习的有利工具。