Final answer:
The structure being described is the uterus. It nourishes and supports the growing embryo and undergoes significant changes during pregnancy.
Step-by-step explanation:
The structure being described is the Uterus.
The uterus is the muscular organ that nourishes and supports the growing embryo. It has three sections: the fundus, which is the portion superior to the opening of the uterine tubes, the body of uterus, which is the middle section, and the cervix, which is the narrow inferior portion that projects into the vagina.
During pregnancy, the uterus undergoes significant changes to accommodate the developing fetus and support its growth.