Anatomy: Fetus in Utero

Illustration of fetus in utero

Amniotic sac. 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). This protects the fetus from injury and helps to regulate the temperature of the fetus.

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

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

Fetus. An unborn baby from the eighth week after fertilization until birth.

Placenta. An organ, shaped like a flat cake, which only grows during pregnancy. The fetus takes in oxygen, nutrients, and other substances from the placenta and eliminates carbon dioxide and other wastes.

Umbilical cord. A rope-like cord connecting the fetus to the placenta. The umbilical cord contains 2 arteries and a vein, which carry oxygen and nutrients to the fetus and waste products away from the fetus.

Uterus (also called the womb). The uterus is a hollow, pear-shaped organ located in a woman's lower stomach between the bladder and the rectum. It sheds its lining each month during menstruation. A fertilized egg (ovum) becomes implanted in the uterus and the fetus develops.

Vagina. The part of the female genitals behind the bladder and in front of the rectum that forms a canal. This extends from the uterus to the vulva.

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