Core Principles Of Prenatal Development

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Core Principles of Prenatal Development

Prenatal development is the process through which an embryo develops from a single cell

after fertilization to a fetus and then a baby after birth. The process takes approximately 38 weeks

after conception. Immediately after fertilization, a zygote starts developing. It follows a series of

stages before it grows into a baby (Falkner 45). The core principles of prenatal development relate

to the three stages which are the germinal stage, the embryonic stage and the fetal stage.

a. Germinal Stage

The germinal stage occurs in the first fourteen days after fertilization. It occurs immediately

after conception until the zygote implants on the uterine wall. Conception takes place when a sperm

cell and an ovum fuse to form a zygote. Immediately after fertilization takes place and the zygote

is formed, cell division and growth starts taking place. Cell differentiation starts to occur as well.

At this point, the parents’ DNA is passed on to the offspring. The genetic composition and sex of

the baby to be are also determined at this stage (Falkner 47).

In the first week after conception, the zygote cells divide rapidly and multiply. This process

of cell division is called mitosis. Mitosis is a very critical process. Only less than half of the

dividing cells survive after the first 14 days. Continued cell division makes the cells more

specialized and distinct hence different parts of the body are formed (Wolpert 107).

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As cell division goes on, the cells involved in the formation of the placenta, amniotic fluid

and umbilical cord differentiate fully to form the blastocyst. Six to fourteen days after conception,

the blastocyst attaches itself on the uterine wall in a process referred to as implantation. It at this

point that the germinal stage comes to an end hence ushering in the next stage (Falkner 54).

b. Embryonic Stage

The embryonic stage commences immediately after implantation and it takes up to eight

weeks after conception. It starts at the beginning of the third week after conception. Immediately

after implantation, the multi-cellular organism is known as an embryo. Cells continue dividing

rapidly and groups of cells start performing different functions. This process is called cell

differentiation. Blood vessels start growing. The placenta continues to develop too. The placenta

is a structure that provides food and oxygen from the mother to the embryo through the umbilical

cord. It is connected to the uterus (Falkner 60).

This stage plays a very crucial role in brain development. Due to continued cell division,

the neural tube starts developing at an area called the neural plate. The neural tube is supposed to

later develop into the central nervous system which consists of the brain and the spinal cord.

There are signs of the development of the neural tube. They include the appearance of two

ridges along the neural plate. As days pass by, more ridges form and curl inwards thus forming a

hollow tube. After the tube is formed, the cells start forming at the centre too. The tube closes and

brain vesicles start developing. The vesicles finally form various parts of the brain such as the

forebrain, midbrain and the hindbrain (Wolpert 111).

As cell differentiation continues, three distinct layers referred to as the germ layers are

formed through a process called gastrulation. The layers include the ectoderm which is the

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outermost layer, the mesoderm which is the middle layer and the endoderm which is the inner

layer. Continued development of the embryo leads to differentiation of the germ layers into various

body structures. The ectoderm develops into the skin, hair and the brain. The mesoderm forms

muscles, bones and heart tissues. The endoderm develops into the digestive tract, tongue, tonsils

and lining of the lungs.

During the third week, the heart tissues, the circulatory and digestive system develop. In

the fourth week, the brain continues to develop together with bones and facial structures. During

the fifth week, kidneys, eyes and nose also form. During the sixth week, the hands and limbs start

forming. During the seventh week, eyelids, nipples and hair follicles start developing. By the

eighth week, there more distinct internal organs, facial features and heart tissues (Wolpert 115).

As the embryonic stage ends, there are well developed essential external and internal

structures.

c. Fetal Stage

It commences at the beginning of the ninth week until birth. At this stage, cell

differentiation is almost complete and the embryo is now referred to as the fetus. This period marks

more crucial changes in the brain. The neural tube later forms the brain and spinal cord. Synapses

and neurons develop too. It is at this stage that the fetus starts making reflexive motions with the

arms and legs. Sex organs begin to develop and are fully formed by the time the stage ends. The

fetus also increases in weight and length. As the third month ends, the heartbeat becomes stronger

and all the other body parts develop. The brain becomes responsive. The fetus continues to grow

and develop as it awaits its life outside the womb (Bukatko & Daehler 64).

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Conclusion

The prenatal development period occurs in those three principles; the germinal, embryonic

and fetal stage. It involves physical growth and development of the embryo until it has the body

structures and tissues needed in its life outside the womb.

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Works Cited

Bukatko, Danuta, and Marvin W. Daehler. Child Development: A Thematic Approach. Cengage

Learning, 2012.

Falkner, F. Principles and Prenatal Growth. Springer Science & Business Media, 2013.

Wolpert, Lewis, et al. Principles of Development. Oxford UP, USA, 2015.

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