organogenesis

Embryology – the study of early human development

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What is Embryology?

Embryology is a study following each stage of early human development, the so called prenatal development. The name derives from the Greek word “embryo” which means unborn and “logus” which stands for science, therefore this is a science which studies the unborn.

What is a prenatal development?

Embryology analyses all of the processes that form the human being – from the forming of the reproductive cells all the way to the formation of the fetus body and organs.  Prenatal development means the developmental process of forming a fetus from a single cell. The whole process could be derived in two stages. The first one is called organogenesis and the second is the fetal period.

Organogenesis includes the first 8 weeks after conception. It studies the processes of forming the zygote and the organ primordia. The zygote is the diploid cell forming as the result of uniting the male reproductive cell – sperm and the female reproductive cell –  oocyte. Both of those cells are haploid and in their union they form a diploid zygote. This is really important in keeping the specific genome of the particular specie. For example, each human has 46 chromosomes in each of their cells. That means they are diploid or 2n.These chromosomes are homologous and therefore form 23 pairs. Each reproductive cell has 23 chromosomes formed during gametogenesis, therefore they are haploid (n).  This makes it possible when fusing the sperm and the oocyte each with 23 chromosomes to create a 46 chromosome carrying cell – the zygote.

The fetal period includes the time between 9th week of pregnancy until birth. During fetal period cells, tissues and organs keep on differentiating, while the fetus gains weight and increases in size.

It has been proven that different factors can have an influence on prenatal development. More vulnerable to such effects is the stage of organogenesis, because this is the time where each organ forms. During fetal period organs keep on developing but their basic structure is already formed. Factors could have an effect during fetal period as well, but it would not be that strong as in organogenesis.


Why is Embryology important for us?
In the past embryology had more of an observing importance, rather than today where its knowledge is used to take care of different problems during pregnancy. Most of these problems have an impact on the postnatal development as well.  Many experiments and findings in other  sciences are extremely important in Embryology. They have fundamental importance in understanding each process that leads to the forming of a fetus.  Embryology gives us a chance to create better health care strategies, therefore there would be better outcomes in reproduction.  Having more and more knowledge makes it possible to have better techniques for prenatal diagnosis, treatments, solving the problems of infertility, preventing birth defects. A great percent of the abortions and child’s death is caused by birth defects. For example there is a type of numerical abnormality in chromosomes, where the fetus has 47 instead of 46 chromosomes. In such cases a particular pair of chromosomes has not two but three chromosomes. This is called trisomy. Trisomy 13is an abnormality where the fetus has three chromosomes of number 13. More than 90% of the children die before they were even given birth.  
Normal chromosome number and structure