Embryo Development

Embryo Development

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From the date of conception, trough embryo development, till birth, 38 – 40 weeks should pass, in order to be able to say that the baby is mature and that its born fully carried. If there is uncertainty about the date when a baby is conceived, the most probable term for birth is determined. The duration of the pregnancy is calculated from the first day of the last menstrual cycle and then 280 days or 40 weeks are added, which are the duration of a normal pregnancy.

The life of the baby in the womb is called prenatal (lat. Natus, born) or intrauterine (lat. Uterus, womb) – and is divided into three phases:

PhasesPeriod
Germinal0 to 2 Weeks
Embryonic3 to 8 Weeks
Fetal9 Weeks On
Phases of Embryo Developmnent

Just a few hours after fertilization, the egg – now called the zygote, begins to split. When it goes through the Fallopian tube to the uterus, it has already formed a cluster of cells that are almost the size of a grain of rice. This is known as a morula.

After several days, the morula begins to differentiate the outer layer of the cells from the inner cell nucleus. The outer layer is thickened, that is the so-called trophoblast from which the fetus and the placenta of the fetus will develop.

Approximately 12 to 14 days after fertilization, the outer layer of the egg cell gets a fringed surface, by which it is attached to the mucous of the uterus. This is called implantation of the egg cell. At the same time, two cavities are formed in the inner wall of the cell core. A cell layer remains among them, which is differentiated into three embryonic leaves. This is the basis from which the whole child’s organism will develop.

With the implantation of the egg cell on the wall of the uterus and the creation of the basis for development, ends the germinal and begins the fetal phase in the development of the baby.

The embryo grows rapidly. At the end of the first month of the pregnancy, its length is only 1 mm, and at the end of the second month it is already 20 mm long. Along with the weight gain, in the embryo, the first signs of the organs are showing up. Cells are increasingly differentiated among themselves and form various tissues, i.e. functional integrity – organs.

The basic principle in the development of the embryo and later the fetus, is seen precisely in the constant formation of an increasing number of special elements in the human organism – individualization, and in their stronger interconnection in one entity – integration.

Interestingly enough, a similar principle applies to the overall psychological and social development of the child after birth. It is first formed as an individual, developing increasingly individual physical and psychological characteristics – the process of individualization. Later it seeks to become an integrated unit in the human community, to become its member and to put its individual abilities in the service of social interests – a process of integration. When the development of the child’s personality takes place in a natural way, the child at the same time grows into a differentiated individual and adjusts according to the positive aspirations and activities of the community in which it lives. Regarding normal development, both individualization and integration develop simultaneously. The task of the environment, its parents, teachers and others who educationally affect the child, is to enable and support such a development.

Along with the development of individual organs, the first noticeable functions of the embryo appear. The heart is the first organ to begin its function. The basis for the formation of the heart as a fully functional organ, appears in the 3rd month after the conception. During this period, the heartbeat is still in its primitive stage and is not fully formed, and at the same time it is an indication that the fetus is alive. At 7 weeks, bowel movements can be seen, and after 8 weeks, occasional but very weak muscle contractions as well. The muscles around the mouth are activated first, then the cheeks, and from there the mobility spreads to the shoulders, torso, and upper extremities, and finally to the lower extremities.

It is wrong to say that the baby “comes to life” during the fifth month of pregnancy, when the mother feels its movements in the womb for the first time. But that doesn’t mean they’re its first. The baby’s first movements are so weak, that the mother cannot feel them, and they become noticeable when the baby develops some muscle strength.

While the inner organs are formed inside the embryo, the tissue in which the embryo is wrapped starts to form fetus scrolls and placenta. The uvulas from the outer side, that are on the surface of the placenta, start to embed into the blood vessels from the uterus. The uvulas serve to absorb food through the mother’s blood, oxygen and other ingredients that are essential to the baby’s life. They also prevent the mother’s blood from mixing with the baby’s blood and the penetration of various unwanted substances from the mother’s in the baby’s organism.

With the development of the placenta and the onset of its function, the embryo stage in the prenatal development period of the baby ends. At the beginning of the next, fetal stage, the baby is already an independent – autonomous organism with its own blood circulation and metabolism. The baby depends on the mother and together they are a biological unity, but yet, it is clearly separated by the placenta from the mother’s body.

For the onset of the fetal phase, it is characteristic that the fetus has a completely human appearance and keeps it.

The beginning of all organs is created, they now only need to grow, continue to differentiate and become capable of functions that are designed for life support since the birth. For example, the lungs develop much earlier than the child begins to breathe, also at the end of pregnancy the fetus has a fully developed organ of sight, although it cannot see yet. What is characteristic about fetal development is that many organs have been formed to carry out their function earlier than it is possible to activate them. This is a rule in the fetus development and it is called anatomic anticipation of organ functions.

A certain tissue structure must appear in the body, in order to develop an appropriate function. In other words, the baby’s organism is not able to start using a function if its organ is not mature enough. But when the baby reaches a certain degree of maturity, it instinctively demonstrates an interest in starting and using a particular function.

This rule is an essential and important principle in the child’s raising. For a child to be properly raised, it should not be burdened with activities for which it’s not old enough for. One has to wait for children themselves to show interest in an activity, and that is the surest sign that they are capable of exercising that function. Therefore, at that given moment one should not remain passive towards the interest of the child, and it should be encouraged and given the opportunity to develop that function in a form of exercises for improving it. Overall, a man can learn something new only when he’s mature enough for that novelty. The productive exercise of new functions stimulates the maturation of the organism. Human development is a constant interweaving of processes for maturation of the anatomical structure and acquiring of new skills.

The movement of the fetus becomes even stronger. In the 14th week, they can be already heard with a stethoscope and when the babies turn 17 weeks, their movements can also be felt by the mother. Fetal motor functions mature in such a way that the first notable motor reactions of the larger parts of the body turn into more and more precise movements that are provided by the smaller muscle groups. At the same time, even more individual movements are associated and organized in complex movements. And here, in fact, the law on individualization and integration appears.

Already in the 12th week, the fetus reacts to external stimuli with reflective movements. Simple reflexes grow into defensive reactions – complex limb movements, when they are experimentally irritated. Such experiments are usually performed on fetuses that have been surgically removed due to the mother’s disease or are born prematurely. The 20 week-old fetus is already shows movements in the chest area and imitates breathing. In the 25 week, the child can already produce a very weak voice. Shortly after the appearance of the motor function appears the sensation. By the 10th to 12th week, the child acquires the ability to react to stimuli of the skin and mucous membranes, firstly on the lips and nostrils. Later the sensitivity to mechanical stimuli spreads concentrically to the periphery of the body. Aside from the sense of touch, the heat sensitivity differences appear, especially to the cold. The feeling of pain in the fetus is poorly developed.

At the end of intrauterine period in life, other senses such as taste,  smell, sight and hearing are fully developed. But those senses of the fetus remain passive as there aren’t proper stimuli yet that would have activated them, and they are activated as soon as the baby is born, although in newborns they are not as sharp as they would be later in life. However, the baby is able to distinguish from: sweet, salt and bitter, frowns to sharp odors, reacts to light narrowing the pupils and blinking, and shivers from a sudden stronger sound.

So, the baby is born with the ability to receive and register irritations from the environment and react to them. Now it depends on it to adapt and harmonize these abilities to the environment and its needs and demands. After the birth, the child continues to grow – a period of maturation, which lasts for years. Along with the maturation, the child will acquire various skills. Along the way, it will recognize life in its environment by adjusting the inherited traits of the specific conditions to it. It is the process of developing conditioned responses in the child to the events around it. This natural maturation of various inclinations, opportunities, needs and abilities is constantly combined with learning, adaptation and gaining experience. Everything is listed in an indivisible whole, and this is the essence of the child’s growth.


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