ANATOMY

Detailed explanation-1: -An embryo is defined as any organism in a stage before birth or hatching, or in plants, before germination occurs. Embryology refers to the development of the fertilized egg cell (zygote) and its differentiation into tissues and organs.

Detailed explanation-2: -Topic: Embryogenesis. The early stages of embryonic development, such as fertilization, cleavage, blastula formation, gastrulation, and neurulation, are crucial for ensuring the fitness of the organism. Fertilization is the process in which gametes (an egg and sperm) fuse to form a zygote.

Detailed explanation-3: -The first stage in vertebrates is called neurulation, where the neural plate folds forming the neural tube (see above). Other common organs or structures that arise at this time include the heart and somites (also above), but from now on embryogenesis follows no common pattern among the different taxa of the animalia.

Detailed explanation-4: -When the early embryo consists of only two tissue layers, ectoderm and endoderm, a longitudinal thickening appears as the result of multiplication of the ectodermal cells. This thickening, the primitive streak, gives rise to the notochord and to the third basic layer, the mesoderm.

Detailed explanation-5: -All vertebrate embryos have gill arches, notochords, spinal cords, and primitive kidneys.