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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Ascending aorta

Ascending aorta, anterior view
Ascending aorta

UPDATED: The ascending aorta is the first and most proximal portion of the aorta. About 5 cm. in length and 3 cm. in diameter at its origin, its proximal end begins at the superior aspect of the outflow tract of of the left ventricle, at the ventriculoaortic junction. 

The ascending aorta ends superiorly at an imaginary horizontal plane (blue dotted line) that passes through the sternal angle (of Louis), continuing distally with the aortic arch. This is an important anatomical landmark, as many surgeons use as the superior border of the ascending aorta an oblique plane that passes proximal to the brachiocephalic trunk (yellow dotted line). Although this landmark could be useful in surgery, it is not anatomically correct.

Since the sternal angle (of Louis) also indicates the superior border of the pericardial sac, it can be said that the ascending aorta is completely intrapericardial, and in surgery the pericardial sac should be the anatomical landmark used to separate the ascending aorta from the aortic arch.

From its point of origin at the ventriculoaortic junction, the aorta presents with a dilated region where the aortic valve is located. The aortic valve is one of the two  semilunar valves of the heart, and the dilation of this region is caused by the presence of the sinuses of Valsalva. This dilated bulbous segment is known as the aortic root.

The dilated, sinus portion, or aortic root segment of the ascending aorta continues superiorly with the tubular portion of the ascending aorta. The area of transition between these two components is marked by a sharp crease known as the sinotubular junction (STJ). The dilation of the aortic root is caused by the presence of the sinuses of Valsalva, named after Antonio Maria Valsalva (1666 - 1723).

The tubular portion of the ascending aorta ascends with an inclination anteriorly and to the right. The ascending aorta presents with a slight anterior bulge causing the transverse section of this aortic segment to be slightly oval.

Only two arteries arise from the ascending aorta, both usually at the aortic root segment, just inferior to the STJ. These are the right coronary artery and the left coronary artery. There are anatomical variations where only one, or up to five different coronary arteries have been described.

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