Implantation

Implantation is the process of an embryo attaching to the inner lining of a woman's uterus. It typically occurs 6-12 days after fertilization of the egg by a sperm cell. The embryo, now known as a blastocyst, is made up of two distinct cell types: the outer layer, called the trophoblast, and the inner cell mass, which will eventually form the fetus. The implantation process begins when the blastocyst hatches out of its protective shell and makes contact with the endometrium, the inner lining of the uterus. During this contact, the trophoblast begins to secrete enzymes that break down the endometrium and allow the blastocyst to penetrate into the endometrial lining. The trophoblast also secretes molecules that prevent the mother’s immune system from rejecting the embryo. Once the embryo has penetrated into the endometrium, it begins to attach itself to the uterine wall and develop a placenta. The placenta serves as a vital connection between the mother and the developing embryo, providing it with oxygen, nutrients, and hormones.