Brain originates from which germ layer

Which extraembryonic membrane in humans prevents desiccation of the embryo inside the uterus?

The minimum number of barriers present between foetal and maternal blood is present in which type of placenta?

The yolk plug of gastrula represents in the later stage its

How many eggs do you think were released by the ovary of a female dog which gave birth to $6$ puppies?

What is true about cells during cleavage