Question

For the proper implantation to occur, the zona pellucida layer of the zygote has to be removed. Which of the following is the most suitable site for the complete loss of zona pellucida layer?

• A. Ovary
• B. Fallopian tubes
• C. Uterus
• D. Cervix

Answer 1

The correct option is C Uterus

For proper implantation to occur, the zona pellucida layer of the zygote has to be removed. It is a glyco-proteinaceous layer. It encloses within itself the blastocyst which is capable of implantation. The implantation is possible only by the outer layer of trophoblast cells present in the blastocyst. So, the blastocyst has to lose the zona pellucida layer in order to expose the trophoblast cells. As we know the most suitable site for implantation is the uterus, so the complete loss of the zona pellucida layer is achieved when it reaches the uterus.
If in case the zona pellucida layer is lost in any other part except the uterus, it may lead to a phenomenon called ectopic pregnancy. The pregnancy is termed ‘ectopic’ when the implantation occurs at any site other than the uterus. Ectopic pregnancies can be very dangerous and life threatening. These implants have to be surgically removed to save the life of a person.
Implantation in the ovary is called ovarian pregnancy.
Implantation in the fallopian tubes is called tubal pregnancy.
Implantation in the cervix is called cervical pregnancy.