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 | 18th 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.

Answered by Sivanand Patnaik | 20th May, 2018, 11:54: AM