Which of the following gets embedded in the endometrium during implantation?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → Blastocyst
Option (1) Zygote — Incorrect. The zygote forms in the oviduct and starts dividing (cleavage) as it moves towards the uterus.
Option (2) Morula — Incorrect. The morula (8–16 cells) keeps dividing and becomes a blastocyst before it embeds.
Option (3) Blastocyst — Correct. Its outer trophoblast attaches to the endometrium, the uterine cells cover it, and it becomes embedded. This is implantation.
Option (4) Embryo — Incorrect. The embryo forms from the inner cell mass after implantation.
NCERT Extract:
Fertilisation and Implantation – “… The trophoblast layer then gets attached to the endometrium and the inner cell mass gets differentiated as the embryo. After attachment, the uterine cells divide rapidly and covers the blastocyst. As a result, the blastocyst becomes embedded in the endometrium of the uterus (Figure 2.11 step H). This is called implantation and it leads to pregnancy.”
