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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Atrium

Heart model - LAO cranial view [UPDATED] The term [atrium] is Latin, its plural form is [atria]. The atrium was the center hall of a Roman home, around which the rest of the rooms opened. Since the atrium was the first area of the house that was entered once passing through the front door, the term [atrium] has been used to describe the "entrance hall', such as the atrium of a hotel. The atria are the two superior chambers of the heart. (see image, items "A=right atrium" and "B=left atrium")

An interesting question is why are the atria called so, since they are part of the heart, and not just the entrance?. The reason is that early anatomists considered the heart to be composed only by the ventricles. The atria were then chambers where blood would wait before entering the "heart proper", ergo [atria].

Each atrium has a smooth wall (sinus venarum) and a muscular extension akin to a closed-end bag. These are the atrial appendages or auricles. Anatomically they are quite different. The right atrial appendage communication or opening to the right atrium is wide and allows blood to easily flow from and to the atrium. On the contrary, the left atrial appendage has a very small opening (ostium) and its morphology is convoluted with lobulations and a complicated mesh of atrial muscle wall.

The very structure of the left atrial appendage is quite conducive to the formation of clots in atrial fibrillation (AFib). These anchored clots (thrombus/thrombi) can detach and become free clots (embulus/emboli) that will enter the blood stream, pass into the left ventricle, then though the aortic valve, and then pass into the ascending aorta and main circulation. Unfortunately, two of the first arteries that arise from the aorta are the common carotid arteries that take blood to the brain and these thrombi can cause a brain stroke.

Personal note: On November 7, 2023 Dr. Randall K. Wolf invited me to a seminar where we reviewed the anatomy of the left atrial appendage, the problems it can cause in atrial fibrillation as a cause for stroke, and the reasons for its exclusion in AFib surgery. 

Image property of:CAA.Inc.Photographer:D.M. Klein