What are Teratogens

 

The birth of a baby is miraculous. From one moment to the next, there is an additional person in the room. This birth represents all of the amazing  and complicated pieces of what makes a human being. It represents 40 weeks of exponential change, largely invisible to the world outside the womb. It seems like magic. *Poof* embryo exists, fetus gets bigger, baby is born. The actual activities taking place inside the womb are so much more complicated and magical.

 

Every baby starts with a conception, when half the DNA of the father is carried within the sperm to join half the DNA of the mother in the egg. By the 12th day after conception, the generations of reproducing cells have split into four main groups. One group of cells will become the umbilical cord, connecting the forming embryo to the mother. Another group will form the yolk sac, to produce blood cells for the embryo, and a third group of specialized cells will form the amniotic sac. The fourth group of cells are the ones that will become the embryo. These cells have a very delicate and specific pattern of duplication they will follow from gestational weeks 3 through 8, in order to create cells, and eventually organs, for all of the body systems.

 

This time of specialized duplication is called organogenesis. To get an idea of the true magnitude of change taking place, think about just what is happening the first week of organogenesis, Week 3. During week 3, those cells will specialize and divide to create the neural tube (which will later form the brain and spinal cord), a primitive heart, the first form of kidneys and structures that will become the digestive system. During week 4, these first organs begin to function. By week 5, an embryo is 10,000x larger than the zygote that implanted as week 2 ended. A cell that is damaged during the embryo stage may stop reproducing or it may not complete its function. This damaged cell may reproduce exponentially, as it is programmed to do, proliferating the damage throughout its descendants. An organ damaged while its most basic structure is being created may not be functional when specialization is complete. The more primitive the developing structure, the more damage can be done.

 

It is during organogenesis, while all of the organ systems are being created, that an embryo is most vulnerable to the affects of a teratogen.

 

A teratogen is any factor that can affect the development of an embryo. The teratogen may be completely harmless to a fully-formed human, but the effects on an embryo can be permanent and devastating...

 

What are the different types of teratogens?

 

When are different teratogens most likely to cause damage to different organ systems?