What is morula?

Embryo with 8 to 16 blastomeres .

The correct answer is Option (2)- Embryo with 8 to 16 blastomeres .

Fertilization refers to the process of the fusion of a sperm cell with an egg cell, leading to the formation of a zygote.

Following fertilization, the haploid nucleus of the sperm cell combines with that of the egg cell, resulting in the formation of a diploid zygote. The zygote initiates mitotic divisions while traveling through the isthmus of the oviduct, a process known as cleavage. These divisions give rise to 2, 4, 8, and eventually 16 daughter cells called blastomeres.

The embryo with 8 to 16 blastomeres is called a morula . The morula continues to divide and transforms into blastocyst as it moves further into the uterus. Within the blastocyst, the blastomeres are organized into two distinct layers: the outer layer referred to as the trophoblast and an inner group of cells attached to the trophoblast known as the inner cell mass. The trophoblast layer becomes attached to the endometrium, while the inner cell mass differentiates into the embryo.

Following attachment, the cells of the uterine lining undergo rapid division, enveloping and embedding the blastocyst within the endometrium of the uterus. This crucial process is termed implantation, and it marks the onset of pregnancy.