Stages of Embryo Development
Emrypo development stages are given below:
- Development of embryo begins with the fertilization of an ovum (egg cell) by a sperm, resulting in the formation of a single diploid cell known as a zygote.
- The zygote undergoes series of mitotic divisions without any significant growth (a process termed as cleavage) to form a structure termed as morula.
- By a process called blastulation, the morula develops into a structure called as blastula, which eventually develops into a structure called as gastrula by a process called gastrulation, when pluripotent stem cells differentiate into the three germ layers:ectoderm, mesoderm and endoderm. The ectoderm gives rise to the skin and the nervous system. The mesoderm is responsible for the development of numerous cell types like muscle, bone, and connective tissue. Endoderm layer become the linings of the digestive and respiratory system, and form organs like liver or pancreas.
- The gastrula further undergoes development which includes organogenesis i.e., formation of organs.
- Finally, the embryo migrates to the uterus and attaches to the wall of uterus. This phenomenon is called implantation. In due course of time, the implanted embryo develops different body organs such as the eyes, hands, heart, lungs,legs, etc.
- A completely developed embryo is called a foetus. This entire period is known as pregnancy. Once the foetus is fully mature, the mother delivers the baby.
Viviparous and Oviparous Embryo Development
Oviparous and Viviparous are two categories of animals divided based on embryo development. Oviparous animals reproduce by laying eggs that mature and hatch in the external environment and Viviparous animals hold fertilized eggs inside their bodies and give birth to their young. These reproductive modes are known respectively as “oviparity” (egg-laying reproduction) and “viviparity” (live-bearing reproduction). The development of an embryo may take place internally in viviparous animals or externally in oviparous animals but the stages of development remain the same.
Table of Content
- Modes of Reproduction
- Oviparity (Egg-laying)
- Examples of Oviparous Animals
- Viviparity (Live-bearing)
- Examples of Viviparous Animals
- Embryonic Nutritional Patterns
- Comparison between Oviparous and Viviparous animals
- Stages of Embryo Development
- Metamorphosis in Oviparous Animals