The first month
A very hard process happens at the first 36 hours right after impregnation in the ovule: it breaks in 2 parts and those break down into 4 parts during the next 24 hours. So through this way at the end of the seventh day they become 16. It looks like a currant from its appearance. Yet it doesn’t change its size (it’s no bigger than in the early days and has 0.25 mm size) as it doesn’t get any feeding and moves through vaginal channels. As soon as the ovule gets to the womb and sticks to its back wall – it starts to grow quickly. With the help of special tools we can notice that the cells of the ovule become more hard and firm. This is the beginning of the embryo development. And with the help of ultrasound we also can notice a poor pulsation; this is the first sign of blood circulation and hearth-vein system.
The continuous increasing space between fetus and trophoblast (the outer layer of cells of the embryo of placental mammals, which is attached to the uterus wall and absorbs nourishment from the uterine fluids) fills with fluid.
So as the necessary conditions for t he further development already exists next step is to follow for the development of the embryo. The liquid substance around the fetus is to protect the baby from the surrounding of the interior organs of the mother. First of all it is the stable temperature, second the baby is safe from the hits or harms and third it spends all its potential energy on self development.
At the beginning of the 10th day fetus strictly sticks to the wall of the womb.
After that the normal environment for feeding exists. So at the outer cover (trophoblast) some small fringes come out and penetrate into the womb. From that moment the exterior cover is called chorion and the fetus itself called embryo of chorion. This will go up to 8th week, and later chorion become fetus, and we name fetus till the birth.
Most of the people think that the baby starts to develop faster at the late period of pregnancy then in the first days. But this opinion is not correct as during the early period the fetus gain weight and size, which is quite obvious.
As a matter of fact the fastest growth of the baby fetus happens in the first months, especially within first three weeks when the embryo increase its size 100 times. Besides that its goes through the hardest phase of development. From the 10-15th days in the center of fetus ovule the embryo kidney continuously changes its shape from ball shape to oval one.
Over here all cells start to divide into 3 layers: the lowest (endoderm), the middle layer (mesoblast or mesoderm) and the upper layer (ectoderm)
The first one gives the start of the interior organ (hearth, lungs, kidneys and liver).The cells of this layer are built the way that if some get thick some keep the original size. The cell of the second layer turns into interior organs and bone system. That is how cardiovascular system, kidney, muscles and the skeleton appear. The third layer (external layer) cells are necessary for development of the spinal cord and cerebrum, skin and nails.
So on the 16th day the division of the cell into layers finishes and the embryo grows faster. With the help of ultra sound monitoring it is visible that the fetus formed along like convex strip — or span. So this is the basic for the development of the spinal cord and all bone system. At the same a little tube is visible – this is intestines. A little notch near the spine is the neural system.
By the 20th day two veins became a small heart tube, which is the base of the hearth. It started to beat a few days ago. And through this way the fetus develops blood circulation system.
By the 22nd day the embryo grows 1 billion times at once and keeps on growing. Since then it takes an arciform shape.
One of the ends of the fetus a little bit ticker than the other one.
The head and the brain will grow continuously right here. At the end of the second month it is the half part of the embryo. The other end of the fetus is quite thinner and even looks like a small tail. The male and female sexual cells start to develop here, which can be identified by the 15th week by a special examination.
By the 30th day embryo grows up to 4.5 mm. It has sprouts of cardiovascular, digestive and neural system. Chord is well noticeable on the spinal interstice and the heart beats 170-200 beats per minute.
The development and division of the cells of the embryo run this way. This is very complex process which is identical to every one as a rule.
This process is conducted by special kind of cells base on chord surround. They produce special type of substance that helps the cells to develop in appropriate way alongside with continuous changing the shapes and forming new organs. As a part of this process the cells more and more differ from each other by their shape and functions.
