The embryo (or embryo) is a developing organism within the mother. The status of the human embryo persists up to 8 weeks of pregnancy. During this time, the fertilized egg passes the path of development to a body that possesses all the basic morphological features of a person. And after 8 weeks, the embryo is called a fetus.
Development of the human embryo
In the process of development, the human embryo passes through several stages (periods): the period of the zygote, the period of fragmentation of the zygote , gastrulation, the period of isolation and development of organs and tissues.
The period of the zygote (unicellular embryo) is rather short-lived. Immediately after it comes the stage of crushing the eggs - that is, the multiplication of cells called blastomeres. Zygote is already divided on the way from the uterine tube to the uterus. At the stage of gastrulation, the embryo has a bookmark of the nervous system, musculature, axial skeleton.
And then the development of all the basic systems and organs of the future man. From the ectoderm, the skin, the senses and the nervous system are formed. The epithelium of the digestive canal develops from the endoderm, the muscles, the epithelium of the serous membranes and the genitourinary system from the mesoderm, and the cartilage, connective and bone tissues, blood and the vascular system from the mesenchyme.
Heart of the embryo
At the 4th week of pregnancy, the onset of the heart begins. So far, it looks like a hollow tube. The first pulsating movements, the first heartbeat of the embryo appear at the 5th week of pregnancy.
The heart continues to develop, and soon it becomes four-chambered - with two atria and ventricles. This happens on week 8-9. The structure of the heart is somewhat different from the heart of a born little man. It has an oval window between the left and right atrium and the bottlenose duct between the aorta and the pulmonary artery. This is necessary to supply the whole body with oxygen in the absence of an independent
Delayed embryo development
It happens that the embryo lags behind in its development. The lag in embryo development can result in spontaneous abortion. Such phenomena occur when embryos do not reach the stage of fetal development, and the most frequent cause of miscarriages is chromosomal abnormalities.
The main risk factors are the age of the mother and miscarriages and abortions in a woman's history. It is impossible not to mention the influence of alcohol and drugs on the development of the embryo - these factors can also cause retardation of the development of the embryo and its death.