Spinal Confusion

...an attempt to clarify confusing and innacurate information in science articles

Tuesday, February 14, 2006

An Embryo, Defined

An Embryo.

The majority of people agree that an embryo is the first stage of life. They disagree, however, about when that stage begins.

My good friend Don Reed and I spoke for a few minutes the other day and he asked my opinion on the subject. I knew it was an entrapment question, but I couldn't immediately give a coherent response.

This troubled me, so I decided to give the question some thought.

Don proposed a few ideas, none of which I agreed with.

While discussing SCNT, he proffered that the majority of the public believe that an embryo is the product of an egg and a sperm. Did I agree? No offense, but based on the lack of basic reasoning skills prevelant among the public, I prefer not to base my judgement on public opinion.

Don also offered that an embryo isn't an embryo until implantation. Sorry, can't buy that either.

As a writer and former English teacher, it should come as no surprise that Don has a fondness for the English language. One of his most respected and trusted sources of knowledge is Webster's, the dictionary people.

Webster's published a dictionary in 2003 entitled Webster's New World Medical Dictionary. The doctors who contributed to said dictionary run MedicineNet.com, so I consulted with them on embryo. Their response?

Embryo: The organism in the early stages of growth and differentiation from fertilization to, in humans, the beginning of the third month of pregnancy. After that point in time, it is termed a fetus.
Now this wording is a little tricky, so let's take it slowly.

"The organism in the early stages of growth and differentiation"

The organism in the early stages of development. It lists fertilization as one such stage, but never specifies that fertilization is a requirement for an organism to be an embryo.

Some will argue that fertilization -- the union of the male and female gametes -- is a necessary prerequisite for an organism to be an embryo, and therefore a life. One could similarly say that, based on the above definition, an organism that does not reach the fetal stage was never an embryo, and therefore never life.

I will go out on a limb here and say that women who have suffered miscarriages in the first trimester would differ quite passionately.

Fertilization is a process that ends in the creation of a zygote. Likewise, SCNT is a process that ends in the creation of a zygote. A zygote is considered to be, quite reasonably so, an embryo.

Of course, that is my sole interpretation, based on the definition provided by the authors of Webster's New World Medical Dictionary.

But, what if I am wrong? I always consider that to be a realistic possibility.

Consulting another source in the same family, what does Merriam-Webster have to say?

Embryo: 1 a archaic : a vertebrate at any stage of development prior to birth or hatching b : an animal in the early stages of growth and differentiation that are characterized by cleavage, the laying down of fundamental tissues, and the formation of primitive organs and organ systems; especially : the developing human individual from the time of implantation to the end of the eighth week after conception
Apparently, Webster cannot agree with Webster. Is Webster suffering from a multiple personality disorder? A family dispute?

Or, is the definition of embryo not quite settled?