What is the difference between an embryo and a fetus? I have seen these two being used interchangably in texts so I'm confused.

zbeckabee

Embryo weeks 1-8. In humans, a fetus develops from the end of the eighth week of pregnancy, when the major structures and organ systems have formed, until birth. Aug 26 06, 6:08 PM

Brainyblonde

The embryo of a placental mammal is defined as the organism between the first division of the zygote (a fertilized ovum) until it becomes a fetus. In humans, the embryo is defined as the product of conception from implantation in the uterus through the eighth week of development. An embryo is called a fetus at a more advanced stage of development and up until birth or hatching. In humans, this is from the eighth week of gestation. In other vertebrate animals, the embryo develops inside an egg. Invertebrate animals also develop from an embryo. http://en.wikipedia.org/wiki/Embryo Aug 26 06, 6:12 PM