What does the process of cleavage refer to post-fertilization?

The process of cleavage refers specifically to the series of rapid cell divisions that occur after fertilization. This stage begins with the zygote, immediately formed when a sperm fertilizes an egg. During cleavage, the single-celled zygote divides multiple times to form a multicellular structure known as a blastocyst.

Cleavage is characterized by these divisions occurring without significant growth of the cells in between divisions, resulting in smaller cells called blastomeres. This process lays the groundwork for subsequent developmental stages, such as cellular differentiation and implantation. Understanding the pivotal role of cleavage is fundamental as it sets the stage for forming the embryo and the structures necessary for development.

In this context, cellular differentiation, implantation, and formation of the placenta occur later in the development process. Cellular differentiation begins after the cleavage stage as an embryo develops and cells start to take on specific functions. Implantation occurs when the blastocyst embeds into the uterine wall, and the formation of the placenta develops subsequently to support the growing embryo. Hence, while all these processes are essential for embryonic development, they follow the initial process of cleavage.