Embriology, embryologist, embryo - a compendium of science.

Embryology is the branch of science that studies the embryonic development of living organisms: humans, animals and plants. Its polonised name comes from the Greek embryon - meaning embryo - and logos - meaning science. In this article, we will try to provide the most important information concerning both embryology itself and the work of the embryologist, which has a great impact on the development of the human embryo, also known as the human embryo.

Embryology - historical background and importance of the science

Embryology as a science in modern terms developed relatively late, only in the 19th century, but the subject of human sexual development and reproductive organs has intrigued mankind since antiquity[1]. The invention of the microscope during the Renaissance contributed to its later development. Then came the rise of many natural sciences.

Another breakthrough in the study of embryonic development was the discovery of spermatozoa in 1677. However, it was not until 1827 that Karl Ernst von Baer "discovered the egg cell in the ovarian follicle of humans and mammals"[2] and he is referred to as the father of modern embryology.

The 1970s saw another breakthrough in artificial insemination research - in vitro. In 1978, Louise was born in England and became the first person in the world to be conceived using this method.

The above, very abbreviated information, gives a glimpse of the great importance of embryology in embryonic development. Today, this field of science is developing very rapidly and is the basis of many areas of medicine. One of the tasks of embryology and the embryologist is to fulfil the dreams of many parents to conceive a child.

Embryologist - what does he do?

Knowing the nature of the workings of the processes governing embryology makes it possible to increase public awareness of the method of artificial insemination. Thanks to modern embryology, it is possible to study: the formation, development and implantation of embryos, as well as the entire process of foetal development up to birth.

One area of embryology that is particularly important for parents-to-be who decide to in vitro fertilisation and will be qualified for it, is clinical embryology. The work of the clinical embryologist mainly takes place in the embryology laboratory, with the first key task being the preparation of gametes for in vitro fertilisation.

The first step of the clinical embryologist's work with gametes is their appropriate purification. The ova collected from the woman are prepared step by step for fertilisation and also assessed for their maturity[4]. The selected eggs are combined with previously selected and qualitatively assessed sperm. The procedure takes place with the aid of a microscope (which magnifies the image by more than six thousand times with the aid of digital equipment) and an individually selected method of in vitro fertilisation.

The next stage of the clinical embryologist's work is to observe and culture embryos to the blastocyst stage - the final stage of embryo development in vitro. If all goes well, the embryo is prepared for intrauterine transfer. The implementation of the embryo after transfer is the culmination of the responsible and extremely precise work of the embryologist in the IVF procedure.

In addition to this, the clinical embryologist is involved in freezing, storing and thawing embryos for future use. The embryologist's activities also include running a germ cell and embryo bank.

Key support when trying to have offspring

Although the profession of embryology is not very popular, the profession is crucial for couples trying to have a baby. It is therefore worth taking a moment to delve into the subject in order to appreciate the people who help with the IVF process. This will give you a full understanding of what a worker trained in embryology does and why it is so necessary.

Stages of embryo development in the in vitro procedure

We already know what human embryology is and what the work of an embryologist consists of. It is still worth taking a closer look at the stages of embryo development under laboratory conditions.

Before the embryo reaches the blastocyst stage (followed by the transfer of the fertilised cell to the uterus), it is placed in an incubator for several days, where divisions and the various stages of human embryonic development take place.

There are several stages of embryo development in the IVF procedure:

1. Zygote - is formed in the first day after the fusion of female and male gametes;
2. 2-cell embryo stage - when, 24 hours after fertilisation, the zygote divides two cells, this indicates sperm action and good news;
3. 4-cell embryo stage - 48 hours after micromanipulation, there is a further division into four cells, which become blastomeres, i.e. cells arising from the division of the zygote;
4. 8-cell embryo stage - after 72 hours the embryo is already divided into 8 cells;
5. morula - on day four, the resulting blastomeres (12-16) fuse together;
6. early blastocyst - on day five, the embryo reaches its final stage of development, which can determine whether it is ready for transfer to the uterus;
7. Expanding blastocyst - is formed on the sixth day, when the embryo consists of around 100 cells, the protective casing which has been in place up to this point gradually disappears and the embryo can be transferred into the uterus or secured for the future in liquid nitrogen.
8. hatching blastocyst - this is the stage of embryonic development that first occurs in the uterus after transfer; the membrane protecting the embryo has ruptured and the released blastocyst is looking for a place to implant;

[1] H. Bartel, Embryology. Handbook for students, Warsaw 2004, p. 16.

[2] Ibid, p. 20.

Substantive consultation:

dr n. biol. Agnieszka Popow-Woźniak - ESHRE Senior Clinical Embryologist, senior embryologist, head of embryology laboratory