Early Stages:
* Fertilization: This is the moment the sperm and egg unite, forming a single-celled zygote. It's microscopic and indistinguishable from any other cell.
* Cleavage: The zygote rapidly divides into a ball of cells called a morula. It's still very small and lacks distinct features.
* Blastocyst: The morula develops into a blastocyst, a hollow ball of cells. It's about the size of a pinhead and has a distinct inner cell mass, which will develop into the embryo itself.
Embryonic Development:
* Gastrulation: This is a crucial stage where the blastocyst forms three germ layers – the ectoderm, mesoderm, and endoderm. These layers will eventually give rise to all the different tissues and organs in the body.
* Organogenesis: The embryo begins to develop its major organs, including the brain, heart, limbs, and digestive system. It starts to resemble a horse, but still very small and underdeveloped.
* Fetal Development: After organogenesis, the embryo is considered a fetus. It continues to grow and develop, gradually taking on the recognizable features of a foal.
Specific Features:
* Size: Horse embryos are very small during the early stages, barely visible to the naked eye. They grow rapidly, reaching around 1 inch in length by the end of the first month.
* Shape: Early embryos are spherical, but they gradually elongate and take on a more recognizable horse-like shape as they develop.
* Structures: As the embryo develops, key structures such as the heart, limbs, and head become visible.
Note: It's important to remember that horse embryos develop very quickly, and their appearance changes significantly over the course of pregnancy. If you're interested in seeing images of horse embryos, you can find them online through reputable scientific websites or textbooks.