The placenta as the tree of life

The helical course of the umbilical vessels was recorded by Jacobus Berengarius in 1521, and in 1600 Hieronymus Fabricius ab Acquapendente provided the first illustrations in his book De formatu foetu.

Both left and right helices may occur in the umbilical cord; the left:right ratio is 7:1, while absent coiling is considered an indicator of poor prognosis.

Many hypotheses have been formulated over the years to explain the coiling: fetal movements, torsion of the embryo, differential umbilical vascular growth rates, and haemodynamic forces. The left:right ratio has also been compared to left:right handedness and the northern:southern hemispheres, but the origin of umbilical cord coiling is still largely a mystery, as many conditions of the placenta are.1

Classic human anatomic terminology often refers to plants. In the placenta the branching villi are called trunci chorii, rami chorii, and ramuli chorii.

However, the placenta, as is clear from the illustration in De formatu foetu, is an inverted tree, with the branching villi being the roots of the growing embryo (fig 1); furthermore, helical growth is a common pattern in climbing plants.

Comparative physiology with plants may provide new insights into the placenta, and of several diseases in pregnancy, in an “evo-devo” approach.

Fig 1  Illustration of the placenta from Hieronymus Fabricius ab Acquapendente’s De formatu foetu (courtesy of the historical section of the Vincenzo Pinali Medical Library, University of Padova, Italy)

Silvia Chiarelli, professor of pathology, 

Ludovica Sandei, medical doctor

Department of Medicine (DIMED), University of Padova, Italy

[email protected]

Competing interests: We have read and understood the BMJ Group policy on declaration of interests and have no relevant interests to declare.

References

↵Lacro RV, Jones KL, Benirschke K. The umbilical cord twist: origin, direction, and relevance. Am J Obstet Gynecol 1987;157:833-8. doi:10.1016/S0002-9378(87)80067-4