The cluster of developing cells from conception until birth is called an embryo. It begins with the germinal stage, which lasts from conception to implantation of the zygote (fertilized egg) in the lining of the uterus.
During this stage, the zygote undergoes cell division and multiplication, resulting in a mass of cells known as a morula. The morula then becomes a blastocyst, with an outer layer of cells that will become the placenta and an inner mass of cells that will become the embryo.
At the end of the first week after conception, the blastocyst attaches to the uterine lining and the embryonic stage begins. This stage lasts from the third through the eighth week after conception.
During this period, the basic structures of the embryo start to develop into areas that will become the head, chest, and abdomen. The heart begins to beat and organs form and begin to function.
The embryonic period is a critical time for fetal development, and exposure to certain substances or conditions can result in birth defects. For example, alcohol consumption during pregnancy can lead to fetal alcohol syndrome, which can cause physical and cognitive abnormalities in the child.
After the embryonic period, the fetus stage begins nine weeks after conception and lasts until birth. During this stage, the fetus grows and matures, developing features such as hair, nails, and teeth. The fetus also becomes more active, moving and kicking in the womb.
Overall, the development of an embryo into a fetus is a complex and remarkable process that involves the formation of basic structures and organs. It is important for pregnant individuals to take care of themselves and avoid substances and conditions that could harm their developing fetus.