Anatomy: Fetus In Utero

Below you will find some terminology that may help you as you’re reading about pregnancy. The terms relate to organs and body parts that help a woman carry a baby to term.

Amniotic sac is a thin-walled sac that surrounds the fetus during pregnancy. The sac is filled with amniotic fluid (liquid made by the fetus) and the amnion (the membrane that covers the fetal side of the placenta), which protects the fetus from injury and helps to regulate the temperature of the fetus.

Anus is the opening at the end of the anal canal.

Cervix is the lower part of the uterus that projects into the vagina. It is made up of mostly fibrous tissue and muscle and is circular in shape.

Fetus is the name for an unborn, developing baby from the eighth week after fertilization until birth.

Placenta is an organ, shaped like a flat cake that only grows during pregnancy and provides a metabolic interchange between the fetus and mother. Through the placenta, the fetus takes in oxygen, nutrients, and other substances and eliminates carbon dioxide and other wastes.

Umbilical cord is a rope-like cord that connects the fetus to the placenta. The umbilical cord contains two arteries and a vein that carry oxygen and nutrients to the fetus and waste products away from the fetus.

Uterus (also called the womb) is a hollow, pear-shaped organ located in a woman's lower abdomen, between the bladder and the rectum. It sheds its lining each month during menstruation, except during pregnancy. During pregnancy, once the fertilized egg (ovum) implants in the uterus, it becomes the home where the fetus develops into a baby.

Vagina is the part of the female genitals that forms a canal extending from the uterus to the vulva. It is behind the bladder and urethra and in front of the rectum.