What is happening week 1 in a chicken egg?

During the first week of incubation in a chicken egg, several important developmental processes take place:

Day 1:

- Fertilization: If the egg has been fertilized by a rooster, the process of embryonic development begins. The fertilized egg undergoes cell division, forming the blastoderm, which is the precursor to the embryo.

Day 2:

- Formation of the germinal disc: The blastoderm continues to grow and differentiate, forming the germinal disc. This disc consists of three layers: the epiblast, which gives rise to the embryo, the hypoblast, which forms the yolk sac, and the mesoblast, which develops into various tissues and organs.

Day 3:

- Primitive streak formation: A prominent line, known as the primitive streak, appears on the germinal disc. This structure marks the beginning of gastrulation, a process during which the three germ layers are further organized and the basic body plan of the embryo is established.

Day 4:

- Development of neural tube: The neural tube, which will eventually become the brain and spinal cord, begins to form from the ectoderm, one of the three germ layers.

Day 5:

- Heart development: The heart starts to develop as a simple tube-like structure, and blood circulation begins.

Day 6:

- Optic vesicles: The optic vesicles, which will develop into the eyes, appear as outgrowths from the developing brain.

Day 7:

- Limb buds: The limb buds, which will give rise to the wings and legs, begin to emerge.

End of Week 1:

- By the end of the first week of incubation, the embryo has undergone significant development, with the formation of various vital structures and systems. The embryo is still relatively small, but the foundations for further growth and differentiation have been laid.