Implantation is a complex process that involves the attachment of a fertilized egg, called a blastocyst, to the lining of the uterus. This process can be divided into four distinct stages:
1. Apposition:
The blastocyst, after traveling through the fallopian tube, reaches the uterine cavity.
The blastocyst comes into close contact with the uterine lining, called the endometrium.
The outer layer of the blastocyst, called the trophectoderm, interacts with the endometrium.
2. Adhesion:
The blastocyst adheres to the endometrium, establishing a strong connection.
The trophectoderm cells secrete enzymes that break down the endometrial lining, allowing for deeper penetration.
3. Invasion:
The blastocyst burrows into the endometrium, embedding itself within the uterine lining.
The trophectoderm cells differentiate into specialized cells, including the syncytiotrophoblast, which further invades the endometrium.
4. Establishment:
The blastocyst is fully embedded in the endometrium, establishing a stable connection with the mother's blood supply.
The placenta begins to form, providing nourishment and oxygen to the developing embryo.
These four stages are crucial for successful pregnancy, ensuring the embryo's survival and growth.
