Question

Morula is a developmental stage
A) Between the zygote and blastocyst
B) Between the blastocyst and gastrula
C) After the implantation
D) Between implantation and parturition

Answer 1

A sequence of cleavage divisions of the early embryo, beginning with the single-celled zygote, creates the morula. It starts to form a mulberry until the embryo has split into 16 cells, hence the term morula.

Complete answer:
First we should know about morula to answer this question. A morula is an initial embryo composed of 16 cells found within the region pellucida in a solid ball.
Now, let us find the solution from the options-
- Zygote is formed after fertilisation. Zygote undertakes cleavage-called mitotic divisions to create 2, 4, 8, even 16 daughter cells known as blastomeres. Such divisions begin as the zygote passes into the uterus. At the 8-16 cell level, it is called morula and begins to differentiate to form blastocysts.
- In the early embryonic growth of most organisms, gastrulation is a process in which the blastula is restructured into a multilayered form known as the gastrula. Thus, option B is not the correct option.
- The phase of pregnancy in which the embryo conforms to the wall of the uterus is implantation. At this phase of prenatal growth, a blastocyst is named the conceptus. In order to be allowed to grow, the embryo gets oxygen and nutrients from the mother through this adhesion. Thus, option C is not the correct option.
- Parturition implies birth. Childbirth is the climax of pregnancy, in which a child grows within the uterus of a woman. Childbirth is termed labour as well. Roughly nine months after childbirth, pregnant humans go into labour. Thus, option D is not the correct option.

Thus, the correct answer is option (B) between the blastocyst and gastrula.

Note: Within several days after fertilisation, with the development of desmosomes as well as gap junctions, cells on the outer surface of the morula become closely joined together, becoming almost indistinguishable. Compaction is the term used to describe this method.