| A | B |
|---|
| blastocyst | stage of development during which the zygote consists of a ball of cells |
| embryo | stage of development after the fertilized cell implants into the uterus but before the cells take on a recognizable shape |
| amniotic sac | fluid-filled organ that cushions and protects the developing embryo of some vertebrates |
| placenta | organ that develops in female mammals during pregnancy and carries nutrients from the mother to the embryo |
| umbilical cord | structure that connects an embryo to its mother and provides the embryo with nourishment and waste removal |
| trimester | one of three periods of approximately three months each into which a human pregnancy is divided |
| fetus | unborn offspring from the end of the eighth week after conception to the moment of birth |
