Final answer:
Embryonic development starts with fertilization, leading to a series of cell divisions and the formation of a morula and then a blastocyst. This is followed by gastrulation, where the blastula is reorganized into a three-layered gastrula, with each layer differentiating into various tissues and organs. Neurulation comes next, forming the precursor to the central nervous system.
Step-by-step explanation:
Embryonic Development Stages
Embryonic development begins with fertilization, after which the single-celled zygote undergoes a series of divisions known as cleavage. This results in the formation of a morula, a solid ball of cells. As these cells continue to divide, they form a fluid-filled cavity, transitioning the morula into a blastocyst. The blastocyst consists of an inner cell mass with the potential to become embryonic stem cells and an outer layer of cells known as the trophoblast.
The next crucial stage is known as gastrulation, where the blastula reorganizes into a layered structure called the gastrula. This process involves the formation of three primary layers of cells: the ectoderm, mesoderm, and endoderm, each of which will differentiate into different tissues and organ systems. The ectoderm will give rise to the nervous system and skin, the mesoderm to muscle cells and connective tissue, and the endoderm to the internal organs.
Neurulation is the process that follows gastrulation, where the ectoderm folds to form the neural tube, which is the precursor to the central nervous system. Successful completion of these stages is critical for the proper development of the embryo.