At the end of 4 weeks the fruit grew to 1 mm and its size is now like a poppy seed. At this stage of development, the fetus from the fetal egg begins to transform into an embryo. At pregnancy on 4 week the size of a fruit though also tiny, but the embryo feels more confidently and more and more strongly it is attached to a wall of a uterus.
Beginning with this period, a vascular network is produced in the place where the embryo is docked to the uterine wall. These sosudies connect the future baby with his mother, and through them he will not get everything necessary for life and development. When the age of the fetus is 4 weeks, then the embryo begins to develop extra-germ organs, providing its nutrition, respiration and protection. Such bodies include:
- Chorion . An external embryonic membrane that promotes the creation of the placenta, which is fully formed at the end of the twelfth week.
- Amnion . Cavity, which is a fetal bladder, producing amniotic fluid, in which the embryo is located.
- The yolk sac . Until the age of 7 - 8 weeks, he is responsible for the hematopoiesis of the embryo.
How does the fetus look like in 4 weeks?
Many people wonder how the fetus is in 4 weeks. During this period, it looks like a disk that consists of three cell layers - germ layers:
- ectoderm (outer layer), which is responsible for the formation of skin, hair, nervous system, lenses and tooth enamel;
- Endoderm (inner layer), responsible for the formation of the digestive system, liver, thyroid and pancreas;
- mesoderm (middle layer), which eventually evolves into a skeleton, connective tissues and muscles, blood and excretory system, genital organs.
Pregnancy will be visible only at the end of the week, if done hCG-analysis. As for the home test, he is not always able to recognize such an early period, because the woman's urine contains insufficient amount of hormones.