Interesting Discoveries about the Anatomy of the Human Heart
Embryonic Heart Folding Patterns
Written & illustrated by Laura Maaske, MSc.BMC, Medical Illustrator & Medical Animator| e-Textbook Design
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.
Human Heart Formation
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:
Tubular heart of human embryo before 14 days.
Human embryonic heart. 14 day old.
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. He found the heart folding embryo patterns are present in the adult heart. Here is a video explaining Torrent Guasp’s dissection:
“When I looked at the heart for the first time I saw a circumferential basal loop. And then I saw a descending limb and an ascending limb. And they curl around each other at a helix and a vortex, except for the ventricle. And the angles at which they go is about 60 degrees. 60 degrees down and 60 degrees going up, and they cross each other in that way. For years people had wondered why this happened. I realized this is really a spiral. And I began to think about spirals. And I began to understand that spirals are almost the master plan of nature in terms of structure and in terms of rhythm.? if you pick the middle of the spiral up you form a helix. And of course the heart is a helix.” -Dr. Gerald Buckberg, M.D.
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:
[Tweet “Untying the human heart: Your heart is actually a spiral”]
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.
October 29, 2013
Laura Maaske, MSc.BMC, Medical Illustrator & Medical Animator | e-Textbook Designer