Thursday, March 20, 2008
When Does Life Begin? What the Medical Textbooks Say
“Each human being starts his life, his very being, as an ordinary cell called the zygote, measuring less than 0.2 mm in diameter.”
Essentials of Human Embryology, S.M. Bhatnagar et. al., 1983, Orient Longman, India
“The male and female sex cells or gametes…unite at fertilization to initiate the embryonic development of a new individual.”
“Fertilization takes place in the oviduct (fallopian tubes)... resulting in the formation of a zygote containing a single diploid nucleus.”
“Embryonic development is considered to begin at this point.”
“This moment of zygote formation may be taken as the beginning or zero time point of embryonic development."
Essentials of Human Embryology (pp. 1-17)
Larsen, W.J. 1998.
Churchill Livingstone, New York.
"Zygote: this cell results from the union of an oocyte(egg) and a sperm. A zygote is the beginning of a new human being (i.e., an embryo).
Human development begins at fertilization, the process during which a male gamete or sperm ... unites with a female gamete or oocyte ... to form a single cell called a zygote. This highly specialized, totipotent cell marks the beginning of each of us as a unique individual.
The Developing Human: Clinically Oriented Embryology by Moore, K. and T.V.N. Persaud. 1998. (6th ed.), W.B. Saunders Company, Philadelphia. (pp 2-18)