In What Developmental Stage Does the Human Embryo Implant in the Wall

Question

In what developmental stage does the human embryo implant in the wall of the uterus?
A) as a zygote
B) in the morula stage
C) in the blastocyst stage
D) in the gastrula stage
E) during organogenesis

Accepted Answer

Implantation of the human embryo usually occurs during the blastocyst stage, which is around 5-6 days after fertilization. At this stage, the embryo has formed into a hollow ball of cells, with an inner cell mass which will go on to form the embryo itself, and an outer layer of cells called the trophoblast which will form the placenta. The blastocyst then attaches to the lining of the uterus, known as the endometrium, and begins to grow and develop further.