uterus

Hollow muscular organ of female mammals, located between the bladder and rectum, and connected to the Fallopian tubes above and the vagina below. The embryo develops within the uterus, and in placental mammals is attached to it after implantation via the placenta and umbilical cord. The lining of the uterus changes during the menstrual cycle to prepare it for pregnancy. In humans and other higher primates, it is a single structure, but in other mammals it is paired.

In fertilization a sperm fuses with an ovum and produces a zygote. The zygote sinks into the lining of the uterus. It then grows a placenta which brings the fetus's blood close to the mother's blood so that the fetus can obtain oxygen and nutrients. The outer wall of the uterus is composed of smooth muscle, capable of powerful contractions (induced by hormones) during childbirth.