For lab this week, we were instructed to document certain stages of the development of chicken embryos. Before I get started, I decided to learn a little more about the development of this organism. I think this acquired knowledge might help me in the process of capturing significant stages and structures when conducting the lab.
Once an egg is fertilized by a sperm, the embryo will begin to develop after about five hours, forming the zygote. It will then begin cell division and eventually change into the blastoderm. This stage is comprised of eight cells which will develop into 256 cells after just four hours. The embryo, then, differentiates two layers known as the endoderm and ectoderm. The endoderm will eventually turn into the respiratory and digestive systems, as well as secretory organs. the ectoderm will produce the nervous system, sections of the eyes, the feathers, beak, skin, and claws. Eventually, a third layer will develop known as the mesoderm. This layer is important for producing the skeleton, muscles, circulatory system, reproductive organs, and excretory system.
At day one, the embryonic tissue begins to appear; day three, the heart beats; day eight, feather tracks are seen; day thirteen, the body is slightly covered in feathers; and day twenty, the embryo becomes a chick. Before a human embryo even begins to have a heart beat, the chick embryo is fully developed and ready to hatch.
Below is an image of a chick embryo at 96 hours. As you can see, many of the organs of the chick are distinguishable.