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

Jean-Louis Petit

Jean Louis Petit
(1674 – 1750)

French surgeon and anatomist, Jean Louis Petit was born in Paris in on March 13, 1674.  His family rented an apartment at his house to Alexis Littre (1658 – 1726), a French anatomist. Petit became an apprentice of Littre at seven years of age, helping him in the dissections for his lectures and at an early age became the assistant in charge of the anatomic amphitheater.

Because of Petit’s dedication to anatomy and medicine, in 1690 at the age of sixteen, became a disciple of a famous Paris surgeon, Castel.

In 1692, Petit entered the French army and performed surgery in two military campaigns. By 1693 he started delivering lectures and was accepted as a great surgeon, being invited to the most difficult operations.  In 1700 he was appointed Chief Surgeon of the Military School in Paris and in the same year he received the degree of Master of Surgery from the Faculty of Paris.

In 1715 he was made a member of the Royal Academy of Sciences and an honorary member of the Royal Society of London. He was appointed by the King as the first Director General of the Royal Academy of Surgery when it was founded in 1731.

Petit’s written works are of historical importance.  “Traite des Maladies des Os” ( A Treatise on Bone Diseases);  “Traite des Maladies Chirurgicales et des Operation” (A Treatise on Surgical Diseases and their Operations” This last book was published posthumously in 1774. He also published a monograph on hemorrhage, another on lachrymal fistula, and others.

He was one of the first to perform choIecystotomy and mastoidotomy. His original tourniquet design for amputations saved many in the battlefield and the design of the same surgical instrument today has not changed much since its invention by him.

His name is remembered in the lumbar triangle, also called the "triangle of Petit", and the abdominal hernia that can ensue through that area of weakness, the lumbar hernia or "Petit's hernia".

Sources:
1. “Jean Louis Petit – A Sketch of his Life, Character, and Writings” Hayne, AP San Fran Western Lancet 1875 4: 446-454
2. “Oeuvres compl?tes de Jean-Louis Petit” 1837 Imprimerie de F. Chapoulaud
3. Extraits de l'eloge de Jean-Louis Petit Ius dans Ia seance publique de I' Academie royale de chirurgie du 26 mai 1750” Louis A. Chirurgie 2001: 126 : 475- 81

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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: 6346

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.

 Aortic root and aortic valve
Aortic root and aortic valve.
Click on the image for a larger version. 
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
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