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".

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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Latissimus dorsi

Latissimus dorsi muscle (1) - Testut & Latarjet 1931. Public domain
Latissimus dorsi muscle
Click on the image for a larger depiction

The latissimus dorsi muscle is a large, wide, flat muscle on the posteroinferior aspect of the back. It has the shape of a triangle that has a base at the thoracolumbar spine and its apex in the axillary region.

This muscle has a wide origin by tendons that attach to the spinous processes of the lower six or seven thoracic vertebrae as well as those of the lumbar vertebrae, the sacral crest, and the posterior aspect of the external lip of the iliac crest. This created a wide fibrotendinous lamina known as the thoracolumbar fascia. The muscle also attaches to the external surface of the three or four inferiormost ribs and the inferior angle of the scapula.

From here, the muscle fibers converge superolaterally and twist anterosuperiorly to form a quadrilateral tendon that inserts deep into the bicipital groove (Lat: sulcus intertubercularis) of the humerus as shown by number 5 in the accompanying figure. There is sometimes a tendinous extension to the humeral lesser tubercle.

The latissimus dorsi extends, adducts, and medially rotates the shoulder joint, also known as the glenohumeral joint. Along with the teres major muscle they are known as the “handcuff muscles”, as this is the action of these muscles as the hands are brought together towards the back. The latissimus dorsi is innervated by the thoracodorsal (or long subscapular) nerve (C6, C7, and C8).

The Terminologia Anatomica 2 proper name is “musculus latissimus dorsi”. The plural form is “musculi latissimi dorsi”. The name of the muscle is derived from Latin. Since “latum” means “wide”, “musculus latissimus dorsi” means the “widest muscle of the back”, quite a proper name. In other languages this is more evident. In Spanish, the name for the muscle is [músculo dorsal ancho] meaning the “wide muscle of the back”.

The latissimus dorsi is one of the 17 muscles that attach to the scapula. It also forms one of the borders of the lumbar triangle of Petit, potential site for a lumbar hernia.

1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 42nd British Ed. Churchill Livingstone 2021
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015
5. "Trail Guide to The Body" 4th. Ed. Biel, A. Books of Discovery. 2010