that it has long been considered as forming a kind of Gordian knot in Anatomy.
Of the complexity of the arrangement I need not speak further than to say that
Vesalius, Albinus, Haller and De Blainville,
all confessed their inability to unravel it”. –James Bell Pettigrew, 1834-1908
If anyone suggests to you that science, particularly biological science and medicine, is not beautiful and not much more than “a dissection”, as someone once said to me, I could offer you a place to begin… a place of great beauty to point to.
It is one of the fascinating details of evolutionary embryology that I loved learning as a student: the vertebrate heart evolved from a single simple tube into the complex structure we know as our heart. Here is the heart of a human embryo before two weeks:
Here is great old animation depicting the human heart formation:
Circulation functions with a “two-chambered” heart in fish, as you can see in this illustration:
It is a three-chambered in amphibians and reptiles. And it is four-chambered in mammals and birds.
For further comparison, visit these pages which offer comparative imagery: Fish, amphibian, and mammalian hearts, and Fish, amphibian, reptile, and mammal & bird hearts.
During my undergraduate coursework in zoology, this evolution had stuck me as beautiful, that organisms tend towards complexity in their evolution. Later, as a student in biomedical communications at the University of Toronto, I found heart dissections reveal beautifully complicated anatomy compared to what I’d seen in the fish just a few years before.
In fact, while embryologists understood this folding pattern by observing cardiac development, it wasn’t until 2006 that the anatomist Torrent Guasp, using a special technique, dissected the human heart for the first time in history. In this skillful dissection he uncovered the original embryonic tube structure. Here is a video explaining Torrent Guasp’s dissection:
So, for one of my own favorite illustration projects, I began my work by researching this folding pattern, and drawing its reach into the heart. As you can see, the folding works a little bit like a knot, and it is also a two-ended spiral.
I made a sample out of clay and practiced the folding pattern.
And here are my illustrations to reveal the tubular unfolding pattern of the human heart:
As you can see in these illustrations, the adult human heart in its evolved form is a flattened tube, and behaves like a rope as the muscles wrap and squeeze blood. But it is a very complex knot, the dissection of which was not even achieved until the past few years, with Torrent Guasp. How remarkable that a structure so complex can be reduced, backwards, so that its simpler origin is apparent.
Laura Maaske, B.Sc., M.Sc.BMC, Medical Illustrator & Designer
October 29, 2013