Womb

 Womb or also called Uterus is an important part of the female sexual organs (most mammals; including humans). Its shape is similar to pear shape and made mostly of muscles. It is the organ where the fertilized egg (embryo) is kept to grow and develop until the time it is ready to be delivered.

The uterus responds to hormones. Its walls are mostly made of smooth muscle which can expand to occupy the baby and contract at the time of giving birth to push it out.

Reference:

Waters, S. (2008) The Female Reproductive System, 1st edition, New York: The Rosen Publishing Group, Inc.