Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community. We post anatomical, medical or surgical terms, their meaning and usage, as well as biographical notes on anatomists, surgeons, and researchers through the ages. Be warned that some of the images used depict human anatomical specimens.

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A Moment in History

Andreas Vesalius Bruxellensis (1514- 1564)

A Flemish anatomist and surgeon, Andreas Vesalius was born on December 31, 1514 in Brussels, Belgium. He is considered to be the father of the science of Anatomy. Up until his studies and publications human anatomy studies consisted only on the confirmation of the old doctrines of Galen of Pergamon (129AD - 200AD). Anatomy professors would read to the students from Galen's work and a demonstrator would point in a body to the area being described, if a body was used at all. The reasoning was that there was no need to dissect since all that was needed to know was already written in Galen's books. Vesalius, Fallopius, and others started the change by describing what they actually saw in a dissection as opposed to what was supposed to be there. 

Vesalius had a notorious career, both as an anatomist and as a surgeon. His revolutionary book "De Humani Corporis Fabrica: Libri Septem" was published in May 26, 1543. One of the most famous anatomical images is his plate 22 of the book, called sometimes "The Hamlet". You can see this image if you hover over Vesalius' only known portrait which accompanies this article. Sir William Osler said of this book "... it is the greatest book ever printed, from which modern medicine dates" 

After the original 1543 printing, the Fabrica was reprinted in 1555. It was re-reprinted and translated in many languages, although many of these printings were low-quality copies with no respect for copyright or authorship.

The story of the wood blocks with the carved images used for the original printing extends into the 20th century. In 1934 these original wood blocks were used to print 617 copies of the book "Iconaes Anatomica". This book is rare and no more can be printed because, sadly, during a 1943 WWII bombing raid over Munich all the wood blocks were burnt.

One interesting aspect of the book was the landscape panorama in some of his most famous woodcuts which was only "discovered" until 1903.

Vesalius was controversial in life and he still is in death. We know that he died on his way back from a pilgrimage to Jerusalem, but how he died, and exactly where he died is lost in controversy. We do know he was alive when he set foot on the port of Zakynthos in the island of the same name in Greece. He is said to have suddenly collapsed and die at the gates of the city, presumably as a consequence of scurvy. Records show that he was interred in the cemetery of the Church of Santa Maria delle Grazie, but the city and the church were destroyed by an earthquake and Vesalius' grave lost to history. Modern researchers are looking into finding the lost grave and have identified the location of the cemetery. This story has not ended yet.

For a detailed biography of Andreas Vesalius CLICK HERE.

Personal note: To commemorate Andrea Vesalius' 500th birthday in 2014, there were many scientific meetings throughout the world, one of them was the "Vesalius Continuum" anatomical meeting on the island of Zakynthos, Greece on September 4-8, 2014. This is the island where Vesalius died in 1564. I had the opportunity to attend and there are several articles in this website on the presence of Andreas Vesalius on Zakynthos island. During 2015 I also attended a symposium on "Vesalius and the Invention of the Modern Body" at the St. Louis University. At this symposium I had the honor of meeting of Drs. Garrison and Hast, authors of the "New Fabrica". Dr. Miranda

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The aortic root and the aortic valve (2)

Published: Friday, March 16, 2018 07:00 | Written by: Efrain A. Miranda, Ph.D. | Hits: 6946

Aortic root and aortic valve
Aortic root and aortic valve.
Click for a larger image.


This article is a continuation of: The aortic root and the aortic valve (1)

The aortic valve is formed by three semilunar leaflets which are very thin as to be almost transparent.  The attachment of the leaflets is complex, as part of them attaches to ventricular wall, part attaches to the sinusal arterial wall, and even part of them attaches to the membranous interventricular septum and other fibrous structures. Loukas et al state that at “least one third of the circumference of the aortic root is supported by fibrous tissue rather than ventricular musculature”

Each of the three aortic leaflets has a semilunar attachment and shape (hence the term “semilunar valve” used for both the aortic and pulmonary valve, as they have similar shape). The attachment of these three leaflets create a continuous line where the highest points are the three locations where the leaflets attach at the STJ, and the three lower points or “nadirs” form an edge shaped like a three-pronged “coronet”. This coronet is called by many the “anatomical anulus” of the aortic valve, as this is where the fibrous skeleton of the heart forms the “hinges” of the aortic valve.

The leaflets of the aortic valve (as well as those in the pulmonary valve) have a tissue excrescence that can become quite hard at the point where the three leaflets touch on each heartbeat. These are the nodules of Arantius, named after Giulio Cesare Aranzio (1530 – 1589). As a side note, the nodules of the pulmonary valve have a different name. Distally, the aortic leaflets may present a very thin extension that may be cribriform (not shown in the sketch). These are called the lunulae (singular: lunula) as they look like a sliver of moon.

The second component of the base of the aortic root is a ring defined by the lowest portion of each leaflet, the nadir. This ring is called the “virtual basal ring”, is found within the left ventricle and is used as a surgical reference for aortic valve replacement implants.

The three leaflets are found within three dilations of the aortic root, each one called a “sinus of Valsalva”, which extend between the virtual basal ring inferiorly and the STJ superiorly. The presence of the sinuses of Valsalva permits “fluttering” of the open aortic leaflets in ventricular systole. This fluttering of the leaflets allows blood to flow into the sinuses and into the coronary arteries during ventricular systole.

Aortic valve may present with different number of leaflets, as in the case of a bicuspid aortic valve.

The shape of the attachment of the leaflets create two distinct situations:

First, there is a portion of the ventricle related to the leaflets where the ventricle acts as an artery, the aorta. These areas are found inside the sinuses of Valsalva.

Second, there are triangular areas of the aortic root (the interleaflet triangles) where the aortic wall is within the left ventricle and submitted to the pressures and hemodynamics of the left ventricle. These interleaflet triangles have been involved in aneurysms. For simplicity, these interleaflet triangles are not shown in the sketch and are the subject of a separate article in this website.

Note: The image depicts only one complete aortic leaflet. The other one has been transected to show the sinus of Valsalva and the third has been removed to show the attachment or "hinge" of the leaflet. For an anatomical image of the aortic valve click here.

Sources:
1. The Anatomy of the Aortic Root: Loukas, M et al. Clinical Anatomy 27:748–756 (2014)
2. “Extracardiac aneurysm of the interleaflet triangle above the aortic-mitral curtain due to infective endocarditis of the bicuspid aortic valve.” Hori D, et al. Gen Thorac Cardiovasc Surg. 2008 Aug;56(8):424-6
3. “Anatomy of the aortic root: implications for valve-sparing surgery” Efstratios I. Charitos, HS. Ann Cardiothorac Surg 2013;2(1):53-56
4. “The Forgotten Interleaflet Triangles: A Review of the Surgical Anatomy of the Aortic Valve” Sutton JP, et al Ann Thorac Surg 1995;59:419-27

Image property of: CAA, Inc. Artist: Dr. Miranda