Medical Terminology Daily - Est. 2012

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 George Bachman

Jean George Bachmann
(1877 – 1959)

French physician–physiologist whose experimental work in the early twentieth century provided the first clear functional description of a preferential interatrial conduction pathway. This structure, eponymically named “Bachmann’s bundle”, plays a central role in normal atrial activation and in the pathophysiology of interatrial block and atrial arrhythmias.

As a young man, Bachmann served as a merchant sailor, crossing the Atlantic multiple times. He emigrated to the United States in 1902 and earned his medical degree at the top of his class from Jefferson Medical College in Philadelphia in 1907. He stayed at this Medical College as a demonstrator and physiologist. In 1910, he joined Emory University in Atlanta. Between 1917 -1918 he served as a medical officer in the US Army. He retired from Emory in 1947 and continued his private medical practice until his death in 1959.

On the personal side, Bachmann was a man of many talents: a polyglot, he was fluent in German, French, Spanish and English. He was a chef in his own right and occasionally worked as a chef in international hotels. In fact, he paid his tuition at Jefferson Medical College, working both as a chef and as a language tutor.

The intrinsic cardiac conduction system was a major focus of cardiovascular research in the late nineteenth and early twentieth centuries. The atrioventricular (AV) node was discovered and described by Sunao Tawara and Karl Albert Aschoff in 1906, and the sinoatrial node by Arthur Keith and Martin Flack in 1907.

While the connections that distribute the electrical impulse from the AV node to the ventricles were known through the works of Wilhelm His Jr, in 1893 and Jan Evangelista Purkinje in 1839, the mechanism by which electrical impulses spread between the atria remained uncertain.

In 1916 Bachmann published a paper titled “The Inter-Auricular Time Interval” in the American Journal of Physiology. Bachmann measured activation times between the right and left atria and demonstrated that interruption of a distinct anterior interatrial muscular band resulted in delayed left atrial activation. He concluded that this band constituted the principal route for rapid interatrial conduction.

Subsequent anatomical and electrophysiological studies confirmed the importance of the structure described by Bachmann, which came to bear his name. Bachmann’s bundle is now recognized as a key determinant of atrial activation patterns, and its dysfunction is associated with interatrial block, atrial fibrillation, and abnormal P-wave morphology. His work remains foundational in both basic cardiac anatomy and clinical electrophysiology.

Sources and references
1. Bachmann G. “The inter-auricular time interval”. Am J Physiol. 1916;41:309–320.
2. Hurst JW. “Profiles in Cardiology: Jean George Bachmann (1877–1959)”. Clin Cardiol. 1987;10:185–187.
3. Lemery R, Guiraudon G, Veinot JP. “Anatomic description of Bachmann’s bundle and its relation to the atrial septum”. Am J Cardiol. 2003;91:148–152.
4. "Remembering the canonical discoverers of the core components of the mammalian cardiac conduction system: Keith and Flack, Aschoff and Tawara, His, and Purkinje" Icilio Cavero and Henry Holzgrefe Advances in Physiology Education 2022 46:4, 549-579.
5. Knol WG, de Vos CB, Crijns HJGM, et al. “The Bachmann bundle and interatrial conduction” Heart Rhythm. 2019;16:127–133.
6. “Iatrogenic biatrial flutter. The role of the Bachmann’s bundle” Constán E.; García F., Linde, A.. Complejo Hospitalario de Jaén, Jaén. Spain
7. Keith A, Flack M. The form and nature of the muscular connections between the primary divisions of the vertebrate heart. J Anat Physiol 41: 172–189, 1907.


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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.

Sources:
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