In humans,all three germ layers originate from:

The persistence of corpus luteum during pregnancy is due to a hormone known as

The first sign of the growing foetus may be noticed by listening to the heart sound carefully through the stethoscope. The embryo's heart is formed after one month of pregnancy. Which of the following gestation periods is correctly matched?

Blood flowing in the umbilical cord of a mammalian embryo is:

$A$: 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.

The corpus luteum secretes ........