Final answer:
The embryonic stage of development, where the embryo grows, develops specialized cells, tissues, and starts organ formation, lasts from implantation through the eighth week of fertilization.
Step-by-step explanation:
Embryonic Development Stage
The development of the embryo takes place during the embryonic stage, which begins after implantation and lasts through the eighth week following fertilization. This critical period sees the embryo grow significantly in size and complexity. It develops specialized cells and tissues and begins the formation of most organs including the nervous system and vascular structures like the placenta. The three germ layers form, which later differentiate into various tissues and organs, while the embryo's neural tube develops into the spinal cord and brain. Throughout the embryonic stage, the heart begins to beat, and organ systems are structured in their rudimentary forms, setting the essential groundwork for further development and growth.
The stages of embryonic development also include pre-implantation of the zygote and the formation of the blastocyst as it moves towards the uterus. By the end of this stage, marked by incredible cellular division and differentiation, the embryo has established the basic blueprints for all organ systems.