The lens of the eye is derived from which germ layer?

The human embryo is about one inch in length after (in $weeks$)

What is the function of the increased levels of estrogen,progesterone,cortisol,prolactin,and thyroxine in the maternal blood during pregnancy?

Which structure differentiates the gastrula from the blastula?

$A$: If fertilization occurs,the corpus luteum is rescued from regression by human chorionic gonadotropin $(hCG)$,which is produced by the placenta.
$R$: In the first trimester,the corpus luteum,stimulated by $hCG$,is responsible for the production of progesterone.

Blastopore is found in