Question

The placenta is an organ that is made up of a combination of both maternal and fetal tissues. Which of the following forms the maternal portion of the placenta?

• A. Endometrium
• B. Zona pellucida
• C. Trophoblast
• D. Inner cell mass

Answer 1

The correct option is A Endometrium

The endometrium of the uterus forms the maternal portion of the placenta. During implantation, the embryo attaches itself to the endometrial lining of the uterus. For implantation to occur successfully, the glyco proteinaceous layer of zona pellucida has to be removed. Around the 8${}^{\mathrm{th}}$-9${}^{\mathrm{th}}$ day of fertilisation, the trophoblast of the blastocyst gets embedded into the endometrium. Following implantation, chorionic villi rise from the trophoblast. The blood vessels of the cells developing from the trophoblast are called fetal blood vessels. The chorionic villi comes in contact with the endometrial blood vessels (maternal blood vessels). These two types of blood vessels together form the placenta.

The inner cell mass of the blastocyst is involved in the formation of the embryo. So, the cells are also called the embryoblast cells.