Embryology Definition

Embryology is the branch of biology concerned with the development of new organisms. Embryologists track reproductive cells (gametes) as they progress through fertilization, become a single-celled zygote, then an embryo, all the way to a fully functioning organism. There are many subdivisions of embryology, some scientist focusing on human embryos, while others study animals and plants. Evolutionary biologists often use embryology as a means of comparing species, as the development of an organism can give many clues to its evolutionary history. Still other scientists use embryology as a tool to better understand the system or organism they are dealing with, be it conservation of an endangered species or the reproductive disruption of a pest species. Scientists studying human embryology assist with womens reproductive health, and understand the broad scope of issues which can lead to developmental defects and malformations.

Early scientists and philosophers were not ignorant, and were aware of sperm as soon as the microscope was invented. However, there have been competing theories in early embryology. The first notions of embryology are as old as the classical philosophers. Aristotle first proposed the correct mechanism for the development of an embryo, without having a microscope to observe his theory. Aristotle suggested that animals form through the process of epigenesis, in which a single cell divides and differentiates into the many tissues and organs of an animal. However, without evidence, a theory is really only a guess.

A second theory, preformation, gained much traction before the invention of microscopes and more advanced imaging techniques. This idea suggested that the embryo was contained, small but fully formed, inside the sperm. An image of this theory can be seen above. This theory also suggested women were simply vessels to carry the growing child, and that girls came from the left testicle, while boys came from the right. Knowing modern biology, it is obvious that this theory is incorrect. At the time, though, lack of proof and religious overtones into science pushed this rather sexist and equally unproven idea. When the microscope finally was invented, one of the first things people looked at was sperm. The sperm were magnified to the limits of early microscopes, and no fully formed small babies were ever found. But, this failed to fully convince the preformation supporters that epigenesis was the right answer.

It wasnt until 1827 that clear evidence was obtained that female mammals also produce a sex cell, the ovum. The discovery of a female sex cell directly contradicted many aspects of the preformation theory, and led to wider acceptance of the epigenesis theory. Karl Ernst von Baer, discoverer of the ovum, and Heinz Christian Pander then proposed the theory which is still at the heart of embryology today. That theory is the germ layer theory, which postulates that a single cell becomes separate layers of cells as the early organism divides. These germ layers then give rise to the rest of the organism by growing and folding into organs, vessels, and other complex tissues and the cells within differentiate accordingly.

A few more advancements would fully establish the germ layer theory into embryology. The discovery and understanding of DNA led to a more comprehensive understanding of how sperm and egg become a zygote. The development of ultrasound greatly increased the understanding of fetus development in humans, seen in the above image. Many studies were done on simple organisms to understand basic embryology. The flat worm was cultured intensively, as it reproduces sexually and the cells are large enough to watch develop under a good microscope. The fruit fly was also observed extensively, for similar reasons. Studying a polychaete worm, E.B. Wilson developed a coding process to label and understand the movements and divisions of cells during embryogenesis. While the exact process changes depending on the species, this method greatly expedited the understanding of embryology and led to medical and evolutionary science breakthroughs.

An embryologist is a scientist who studies embryology. Any organism that reproduces sexually must create some sort of embryo as it develops into an adult form. An embryologist may study the development of animals, plants, and even fungi. Evolutionary biologists often study embryology as a means of understanding complicated lines of evolution. For instance, all vertebrates including humans go through an embryological phase in which the precursors for gills are present. In humans, these structures develop into structures of the throat. However, the similarity between all vertebrate embryos suggests that all vertebrates arose from a common ancestor which used this form of embryogenesis. A professional embryologist may remain in academia, advancing the science of embryology, or can choose to join the medical profession.

Embryologists are needed anywhere pregnancy is handled, as pregnancy is simply human embryogenesis. Some scientists specialize in disruptions to embryogenesis which result in malformations and disorders. This is called teratology, and covers everything from miscarriages to birth defects. Doctors can specialize solely in embryology and teratology or may choose to cover a broader range of womens health issues.

Many professions employ knowledge of embryology in their practices. Many pharmaceutical companies develop drugs for both fertility and sterility, and the processes of embryology are key to these efforts. Scientists developing insecticides, or ways to deal with other pests, often turn to embryology to battle the reproductive cycles of the organisms. This is often the most cost-efficient way to battle a large pest problem. Others use embryology for the advantage of a species, like the scientists trying to repopulate endangered species. For instance, researchers at several institutions across the United States are teaming up to save the Black-Footed Ferret. They must understand ferret embryology to fully be successful, as well as their behavior, diet, and mating habits. This is a good example of how embryology plays a small but very important role in a larger scientific endeavor.

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Embryology - Biology Dictionary

Behind the scenes at San Antonio IVF, our embryologists maintain the highest level of IVF lab quality, and perform the procedures that lead to the optimal fertilization of eggs, the healthy growth of embryos and the development of successful pregnancies. We are fortunate to have on staff sought-after clinical embryologists and an IVF lab director who are each committed to safeguard the eggs, embryos, and sperm that you entrust to their care.

Our San Antonio IVF embryologists have years of experience performing complex IVF procedures. In addition to conventional insemination in a petri dish, we specialize in advanced services such as laser assisted hatching, intracytoplasmic sperm injection (ICSI), egg and embryo vitrification (ultra-rapid freezing), and embryo biopsy for genetic testing. Our embryologists focus on procedures that affect both male and female infertility, using the latest technologies, including time-lapse photography to assess embryonic development.

Our advanced reproductive technology (ART) laboratory was designed to exact standards, and outfitted with incubators, micromanipulators, and micro-surgical lasers to create the optimal environment for embryonic growth and development. When genetic materials pass through the doors of San Antonio IVF, our embryologists become their caretakers.

The IVF lab, located in the Stone Oak area of San Antonio, consists of over 4000 square feet of customized air filtration systems, microscopes, high definition video systems, and state-of-the-art incubators, each unique to our purpose of sustaining new life.

Our embryologists job starts with an assessment of the male partners sperm. We evaluate every specimen for concentration (the number of sperm present in each cc of semen), motility (the percentage of sperm that are alive and swimming), and normal morphology (the percentage of sperm that have a normal shape). We then choose the best sperm preparation technique to use so that we can get the greatest number of normally shaped, motile sperm to add to the eggs.

Once the eggs have been retrieved, they must be identified, removed from their surrounding cells, and placed into culture so that they can continue to mature in the laboratory. Approximately 5-6 hours after retrieval, several thousand moving sperm are either added to a droplet of culture media containing each egg (insemination), or in cases where the sperm specimen is not of very good quality a single sperm is actually injected directly into each egg by our embryologists using a tiny needle directed by robotically controlled instruments (ICSI). These eggs are then returned to their incubator for 18 hours of development, during which time fertilization hopefully occurs.

Over the course of the following week, while our embryologists monitor and maintain the culture media, gas atmosphere, humidity and temperature levels in the incubators that house the embryos, the embryos begin to divide and develop. They regularly assess embryonic growth checking often enough to make sure the embryos are meeting their developmental milestones, while not checking too often so that the environment within each incubator remains optimal.

A Week in the Life of an Embryo

Day 1: After documenting fertilization, each embryo is placed in culture media that mimics the environment normally found in the fallopian tube.

Day 2: Embryos are allowed to continue growing without being disturbed.

Day 3: Embryonic development is assessed and a decision is made about next steps. In most cases, we will return the embryos to the incubator where they will continue to grow. In rare cases, we consider embryo transfer, or even embryo biopsy on day 3. If we are going to do your embryo biopsy on day 3, an embryologist will remove a single cell from each viable embryo for preimplantation genetic screening (PGS) or diagnosis (PGD) at this time.

Day 4: Embryos are allowed to continue growing without being disturbed.

Day 5: Aside from Day 1 when we confirm fertilization, Day 5 is perhaps the most important day in an IVF cycle. Day 5 is the first day that embryos reach the critical blastocyst stage. If we are planning on doing a fresh embryo transfer, this is the day that it most often occurs. If, on the other hand, we are planning on freezing all embryos, this is the first day that we start this process. In addition, for those patients who desire genetic testing of their embryos, this is the first day that we start to perform embryo biopsies as well.

Days 6 and 7: Embryos are reassessed for vitrification (freezing) and biopsy (if indicated).

An Embryologists Role in Female infertility

An Embryologists Role in Male infertility

Embryologists at San Antonio IVF play a significant role in increasing the chance for successful conception despite male or female infertility factors. Your embryology team at our San Antonio IVF facility treats each specimen as they would a patientwith care, concern and the highest level of professionalism.

Contact San Antonio IVF for more information regarding our laboratory procedures, personnel, and latest successes. We are committed to providing the highest quality, evidence-based IVF lab services by our world class embryologists and andrologists.

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Embryology - San Antonio Fertility

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"embryology." YourDictionary, n.d. Web. 17 March 2019. <https://www.yourdictionary.com/Embryology>.

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embryology. (n.d.). Retrieved March 17th, 2019, from https://www.yourdictionary.com/Embryology

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