Placenta acts as an

In the simplest type of placenta,the foetal blood is separated from the maternal blood by six barriers. How many barriers are lost in the human placenta?

Which of the following statements is true regarding cleavage?

Which structure differentiates the gastrula from the blastula?

If both ovaries are removed from a pregnant human female in the first trimester of pregnancy,then it will lead to:

Human placenta is derived from