CBSE Class 12-science Answered

PLEASE have a WELL LABELLED DIAGRAMMATIC STEP BY STEP REPRESENTATION OF the different stages of EMBRYONIC DEVELOPMENT and brief explanation for eaach diagram and its labelling

Asked by pardeepkumar2281 | 18 May, 2018, 09:37: PM

Expert Answer

1. Stage of fertilization

The female gamete or the egg comes in contact with the male gamete or the spermatozoa inside the female reproductive system either through natural course of intercourse . Normally it occurs during her ovulation, when a woman releases her mature egg or ovum to the fallopian tube. Some women release two eggs (in case of fraternal twins) as well. If the sperm happens to reach the egg during its grand opening, it enters into the egg and a zygote is formed within 24-48 hours.

2. Blastocyst Stage

As soon as the zygote/embryo is formed, the cells within keep developing constantly. This complex form of development is called blastocyst. A blastocyst has two layers of cells-inner cells and outer cells. The inner cells form into muscles, bones, blood and other body parts whereas the outer cells grow into Placenta at a later stage. The Blastocyst is coated with a jelly like protective layer called zona pellucida, which helps the Blastocyst to grow effectively. When the cells within the Blastocyst multiply themselves effectively, the zona pellucida gets tighter and breaks accordingly.

3. Implantation of Blastocyst

After the removal of zona pellucida, the blastocyst enters the uterus and implants itself to the mucus membranes of the uterus. The inner tissues of the uterus and the outer linings of the Blastocyst help in developing the placenta.

4. Development of embryo

After the blastocyst completes its implantation in the inner linings of the uterus, it turns into an embryo. This is the stage where the body of the baby starts developing their form. Mouth, throat, lower jaw, blood circulation system, heart tubes etc. start developing. The ears, arms, legs, spinal cord and everything start to form and fetus development starts from this stage.