The hormone that prepares and maintains the uterus during pregnancy is secreted by

Mammalian embryo is directly surrounded by

The narrow middle part of the epididymis is called

Give the name of two hormones $A$ and $B$ in the figure given below

$A$ : Blastocyst undergoes gastrulation to produce the three germinal layers.
$R$ : This involves cell movements (morphogenetic movement) that eventually help to attain new shape and morphology of embryo