Laboratório de Tecnologia Educacional BIBLIOTECA DIGITAL               DE CIÊNCIAS

This illustration depicts three different stages of embryonic development regarding two species: a fish and a chicken, as shown on the drawing. Fish have only the yolk sac as extra-embryonic tissue. These structures in chicken comprise, besides the yolk sac, the amniotic cavity, chorion and allantois.

Schematical representation of the in vitro fecundation process in human beings: It is a resource used in cases of patologias as damnification in the Tubes of Falópio, harming the transport of óvulo, or little production of spermatozoon for the man. After hormonal stimulation, the mature ovule is collected of the ovary and placed in a test tube contend sperm. The fecundation occurs and after a series of cellular divisions, the originated embryo is implanted in the uterus.