What are the stages of embryonic development?
Stage 1 – Fertilization
In its most basic form, fertilization is the union of the female gamete (egg) with the male gamete (spermatozoa). This union can occur naturally or through an Assisted Reproductive Technique (ART), but it results in a “zygote” in either instance.
Fertilization can occur anywhere between 24-72 hours. Following successful fertilization, the zygote migrates to the uterus and splits into the following stage, resulting in the formation of a blastocyst.
Stage 2- Blastocyst Development and Implantation
The embryo is formed from a tiny collection of cells that divide constantly inside a complex structure known as a “blastocyst.” It is made up of inner cells, exterior cells, and fluids. The zona pellucida is a protective coat that surrounds the blastocyst while it matures, much like an eggshell. In the following stage, the outer cells located beneath this cover form the placenta. The blastocyst’s inner cells come from the tissues, bones, muscles, skin, liver, and heart. All of these modifications occur before to implantation in the uterus.
Stage – 3 Embryo Development
After the implantation, the blastocyst evolves into a structure called an embryo. At this stage, most of the internal organs and external structures develop. Below are the organs and systems that develop:
- The mouth, lower jaw, throat
- The blood circulation system evolves
- Heart tube creation starts.
- Ears and eyes start to grow.
- Arms, legs, fingers, toes are shaped.
- The brain, spinal cord, digestive tract and sensory organs start developing.
- The cartilage will be replaced by the initial bones.
Stage – 4 Fetal Development
The embryo develops into the fetal stage at the conclusion of fertilization. The fetus is far more durable than the embryo. As a result, the chances of miscarriage are lower at this point. After the second trimester, the fetus can respond to sounds and grows to be 12 to 14 inches long. The fetus is termed a baby around the eighth month, and it can see and hear, albeit its respiratory system is not fully developed.