The Biology Book: From the Origin of Life to Epigenetics, 250 Milestones in the History of Biology (2015)

Placenta

Aristotle (384–322 BCE), Galen (c. 130–c. 200), Leonardo da Vinci (1452–1519), William Harvey (1578–1657)

1651

Interest in the mysteries, importance, and functions of the placenta goes back to ancient sources and scholars and continues to the present day. In Egypt, a sculpture depicts the royal placenta, with an attached umbilical cord, and refers to it as the Pharaoh’s “soul” or “secret helper.” The kingdom’s success was thought to be dependent upon the sovereign’s health and preservation of his soul. The Hebrew Bible refers to the placenta as being the “Bundle of Life” and “External Soul.” The placenta (from the Greek “flat cake”) aroused the interest of Aristotle and Galen, the greatest scholars of ancient times. In about 340 BCE, Aristotle initiated examination and naming of the membranes surrounding the fetus, but because of differences among species and his studies using animal subjects, some of his incorrect conclusions were perpetuated for over a millennium.

In about 1510, Leonardo da Vinci focused his genius on depictions of human anatomy, including the fetus. These drawings included the uterus with its blood vessels, fetal membranes, and umbilical cord. He also stated that fetal blood vessels were not continuous with that of the mother, an ongoing subject of question and conjecture dating from ancient times to the eighteenth century. In his 1628 medical classic De motu cordis, William Harvey provided the foundation for our modern understanding of the physiology of the circulatory system and heart.

In 1651, Harvey extended these studies to consider, in detail, fetal circulation and its relationship to the mother. He also raised a very basic question: How does the fetus survive and breathe in the mother’s womb for many months and yet, perishes within a very short time after delivery if unable to breathe? Since mother and fetus have two separate circulatory systems, he postulated that fetal nourishment and air are provided from the fluid within the amniotic sac surrounding the fetus. We now know that from the fourth week of development until birth, placental circulation carries nutrients, respiratory gases, and waste materials between the embryo, fetus (after the ninth week), and the mother.

SEE ALSO: Leonardo’s Human Anatomy (1489), Harvey’s De motu cordis (1628), Ovaries and Female Reproduction (1900), Progesterone (1929).

This engraving from the Usual Medicine Dictionary (1885) by Dr. Paul Labarthe shows a fetus about to be born.