In: Anatomy and Physiology
A woman has a mutation that causes the zona pellucida to be tough and not disintegrate. How would this affect her fertility? Explain.
In the humans beings, after the fertilization occurs the embryo continues to develop within the zona pellucida for approximately five days. Around day 5, the normally developing embryo breaks out of the zona pellucida in a process called hatching. For this to occur successfully, the zona pellucida must thin and eventually tear to allow the embryo to emerge. Once the embryo is free of the zona pellucida, the embryo can then make direct contact with the innermost lining of the uterus - the endometrium. When this contact occurs, the embryo can implant into the uterus and the embryo can continue growing and maturing.
Women with a mutation that causes toughening of the zona pellucida after fertilization may experience infertility because early stage embryos are not able to hatch out of the zona pellucida and implant in the endometrium. In this situation, fertilization and early embryo development may occur normally, but if the embryo cannot implant then the pregnancy will not be successful.
For women undergoing infertility treatment, the challenge of tough or thick zona pellucidas can be treated using a technique called assisted hatching. While the embryo is still in vitro, embryologists use laser-assisted microscopy techniques to breach the zona pellucida. This allows the embryo to hatch shortly before implantation of the embryo into the patient's uterus.