Embryo Development

Embryo Development

From the date of conception trough embryo development till birth should pass 38-40 weeks, in order to be able to say that the baby is mature and that is born fully carried.

Due to incomplete certainly with 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, 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:

  • Germinal – from 0 to 2 Weeks
  • Embryonic – from 3 to 8 weeks
  • Fetal – from 9 weeks on

Germinal Phase


Just a few hours after fertilization, the egg – now called the zygote, begins to split.

Zygote Day1/Day3


When it comes across 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 so called Morula.

Zigota at Day 5 – 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 fringed surface, by which it is attached to the mucous of the uterus. This is called implantation of the egg cell.

Blastocyst attached to uterus
Morula after 12-14 days – Blastocyst attached to the uterus


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.

Important to remember

Embryonic Phase

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

The embryo is growing 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, 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 their 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 he/she lives.

Regarding normal development, both individualization and integration are developing in parallel.

The task of the environment, his parents, teachers and others who educationally affect the child is to enable and support such a development.

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 starts to embed in to 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 from mixing the mother’s blood with the baby’s blood and penetrating various unwanted substances from the mother’s in the baby’s organism.

Fetal Phase

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 sight organ, although it cannot see yet.

About fetal development It is characteristic 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, which means that 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 essential and important principle in child’s raising.

For a child to be properly raised, they should not be burdened with activities for which they are not old enough.

One has to wait for the 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 they should be encouraged and given the opportunity to develop that function in a form of exercises for improving that function.

Overall, a man can learn something new only when is mature enough for that novelty, but productive exercise of new functions stimulates the maturation of the organism.

Human development is a constant interweaving of processes for maturation the anatomical structure and acquiring of new skills.

Important to remember

From 10th – 20th Week till Birth

The movement of the fetus became even stronger.

By 10 to 12 weeks the child acquires the ability to react to stimuli of the skin and mucous membranes, firstly on the lips and nostrils and later the sensitivity to mechanical stimuli spreads concentrically to the periphery of the body.

Already at week 12, the fetus reacts to external stimuli with reflective movements.

Recent simple reflexes grow into defensive reactions – in complex limb movements, when experimentally irritated.

Such experiments are usually performed on fetuses that have been surgically removed due to mother’s disease or are born prematurely.

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 transfer into more and more precise movements that are provided by the smaller muscle groups.

At the same time, ever more individual movements are associated and organized in complex movements.

And here, in fact, the law on individualization and integration appears.

The 20 weeks old fetus is already making moves in the chest area and imitates breathing, and in the 25th week, the child can already produce a very weak voice.

Shortly after the appearance of the motor function appears the sensation.

Beside the sense of touch, the heat sensitivity differences appear, especially to the cold.

Feel of pain in the fetus is poorly developed.

At the end of intrauterine period in life, fully are developed other senses such as taste, smell, sight and hearing.

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: sweet, salt, but bitter, frowns to sharp odors, reacts to light narrowing the pupils and blinking, and shivers from a sudden stronger sound.

Important to remember

Birth and Maturation

So, the baby is born with the ability to receive and register irritations from the environment and react to them.

Now it depends on them 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, they will recognize life in their environment by adjusting the inherited traits of the specific conditions for it.

It is the process of developing conditioned responses in the child to the events around them.

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 child’s growth.

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