请输入您要查询的英文单词:

 

单词 primitive streak
释义

primitive streak

noun Embryology
The faint streak which is the earliest trace of the embryo in the fertilized ovum of a higher vertebrate.After fourteen days, there begins to appear the first traces of what will become the central nervous system of the embryo, the primitive streaks (or the two primitive streaks, since at about this time identical twins may be formed)....
  • Some embryologists and ethicists insist that only after the primitive streak develops can this being be called an embryo.
  • Some have argued that because an embryo can split before the primitive streak appears and form the bases of identical twins, it does not merit the same protection as the embryo that is the basis for a definite individual person.
随便看

 

英语词典包含243303条英英释义在线翻译词条,基本涵盖了全部常用单词的英英翻译及用法,是英语学习的有利工具。

 

Copyright © 2004-2022 Newdu.com All Rights Reserved
更新时间:2025/3/23 16:22:24