Embryo Development

An embryo is the early stage of development in multicellular organisms. It has tissues and organs covered inside Blastocyst. The Embryo develops from the zygote. After a few weeks, the zygote converts into three-four groups of cells.  After eight or nine weeks, the Embryo gets divided into different body parts. After eleven-twelve weeks, this Embryo is called Foetus. The Foetus is the child’s stage when it starts developing into a baby. At this stage, we can recognize the baby as a boy or a girl. 

In animals, the zygote formed after mating divides itself into a package of cells. These stages are termed Gastrulation and Organogenesis, and at a later stage, it develops into an Embryo.  

The Development of Embryo 

The process of human embryo development starts from the fertilised egg. After the egg gets fertilised, which may take two-three days, it becomes a group of nine or ten cells after three days. After almost ten days, the egg is known as Blastocyst. The Blastocyst is a ball-shaped structure that starts dividing itself into cells. It contains a group of cells that later develops into an embryo. This Blastocyst gets implanted into Uterus. Gradually, the cells inside the Blastocyst start developing. After the cells have developed for eight-nine weeks, it is called Embryo when it has developed tissues and organs. So, it can be said that the embryo develops in the uterus. 

The Stages of Developing Embryo

This entire period from Week 4 to Week 8 comes under the process. In these stages, different body parts develop from Embryo.

• Week 4

After the Embryo has completed four weeks, its heart begins to beat, which means that now it has a life of its own. The buds for the arm also appear. It starts developing the pancreas, liver, gallbladder. Spleen, a part of the body present inside the left rib cage that helps fight infection, also appears. 

• Week 5

In the fifth week, the eyes begin forming while the legs buds also appear. The arm buds which appeared in the fourth week now appear as paddles. The blood inside the Embryo starts circulating, and facial features also develop. 

• Week 6

Lungs begin to form from the sixth week onwards. The fingers and toes also grow up this week.

• Week 7

This week, the hair begins to develop. Elbows and toes are also visible after this week. 

• Week 8

After this week, the baby gets a human face and ear-shaped pods are also visible. Partially, it develops into Foetus from now. 

Foetus and later stages

After the Embryo has developed its tissues and organs, it divides the cells into other organs. After about twelve weeks, the Embryo starts developing into a baby. At this stage, it is termed as Foetus. The Foetus takes after the process of the embryo development process. It is a growing, unborn baby who has developing body parts. 

These processes are almost identical in animals too. The embryo development period in animals may vary from animal to animal. It also depends on the shape, size of animals and structure of the Uterus and other inner organs. 

Embryo Development in Plants 

The process of development of Embryo takes place in plants also. It is usually termed Embryogenesis. After the fertilisation through different means, the ovule develops two structures. First is the plant embryo, which develops from the zygote after going through various cellular differentiation processes. The second is the endosperm which later develops into a seed. The processes seem tedious but complete in just four to five hours. After the Embryo has adequately grown, it bursts out to form shoots and roots. The shoot is the part of a plant that is above the ground. It has a stem, leaves and branches. The whole process of development of a plant is Germination. 

Conclusion

From the topic “Embryo Development”, we conclude that a human embryo is a group of cells at the beginning. It forms through the zygote and remains in a thick layer called Blastocyst. It takes about 8 to 9 weeks to grow up into a foetus with a face, limbs and a pumping heart. The process is the same in animals, but the time may vary. Similarly, after the zygote is formed through different means of fertilisation, it develops into an embryo in plants. This Embryo grows in significantly less time to burst out as the shoot and roots of the plant.