Embryonic development
Embryonic Development
Embryonic development (pronunciation: /ɛmˈbraɪ.ɒnɪk dɪˈvɛləpmənt/) refers to the process by which an embryo forms and develops. It begins with the fertilization of an ovum, which then becomes a zygote. The zygote undergoes rapid cell divisions with no significant growth, producing a cluster of cells that is the same size as the original zygote. This stage is known as cleavage.
Etymology
The term "embryonic development" is derived from the Greek words "embryon" (meaning "young one") and "develop" (from the Old French "desveloper", meaning "unwrap, unfurl").
Stages of Embryonic Development
The stages of embryonic development include:
- Zygote: This is the initial cell formed when two gamete cells are joined by means of sexual reproduction.
- Cleavage: This is a stage of rapid cell division without growth.
- Morula: This is an early stage embryo consisting of cells (called blastomeres) in a solid ball contained within the zona pellucida.
- Blastocyst: This is a structure formed in the early development of mammals, containing an inner cell mass and a trophoblast.
- Gastrulation: This is a phase in the embryonic development during which the single-layered blastula is reorganized into a trilaminar (three-layered) structure known as the gastrula.
- Neurulation: This is the process during which the neural tube forms.
- Organogenesis: This is the process by which the ectoderm, endoderm, and mesoderm develop into the internal organs of the organism.
Related Terms
- Embryo: An organism in the early stages of growth and differentiation, from fertilization to the beginning of the third month of pregnancy in humans.
- Fetus: An unborn offspring, from the embryo stage (the end of the eighth week after conception, when the major structures have formed) until birth.
- Gestation: The period of time between conception and birth, during which the fetus grows and develops inside the mother's womb.
- Prenatal Development: The process in which an embryo or fetus (or foetus) gestates during pregnancy, from fertilization until birth.
External links
- Medical encyclopedia article on Embryonic development
- Wikipedia's article - Embryonic development
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