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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Serratus magnus muscle - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Serratus magnus muscle

The serratus anterior or serratus magnus is a is a wide, thin muscle sheet situated on the posterolateral aspect of the thorax and extends between the ribs and the scapula. It is formed by well-defined separate muscular digitations that originate in the external surface and superior aspect of the first superior eight (or nine) ribs. These originating fibers also arise from the fasciae covering the intercostal muscles. This is especially true for the first or most superior digitation which arises from the first and second rib and the intervening external intercostal fascia.

These digitations cover the lateral aspect of the thorax, pass deep to the scapula and converge to insert on the deep aspect of the medial border of the scapula. Some of its fibers may even hug the medial border of the scapula and insert on its anterior aspect. The first digitation is inserted into a triangular area on the ventral surface of the medial scapular angle. The next two digitations spread out to form a triangular sheet, the base of which is directed posteriorly and is inserted into nearly the whole length of the ventral surface of the vertebral border. The lower five or six digitations converge to form a fan-shaped mass, the apex of which inserts into a triangular impression on the ventral surface of the inferior scapular angle. The lower four slips of the serratus anterior interdigitate with the superior five muscular slips of the external oblique muscle.

This muscle receives its nerve supply from the long thoracic nerve, (ventral rami of C5-C7), arising from the roots of C5, C6, and C7 (sometimes absent) of the brachial plexus

The word “serratus” derivates from the Latin word [serro] meaning “saw”. Serratus means “serrated” referring to the multiple tooth-like anterior digitations of the muscle. The plural form for "serratus" is " serrati". The Latin term “magnus” means “great”, “large”, or “mighty”. It points to the fact that this is the largest of three muscles that carry the same name “serratus”. The other two are the serratus posterior superior and the serratus posterior inferior.

The serratus anterior is one of the 17 muscles that attach to the scapula.

Note: The image shown in this article is from “Gray’s Anatomy” by Henry Gray (1918) which is in the public domain. It depicts the serratus anterior in situ and shows the scapula retracted posteriorly.  The scapula is covered on its internal aspect by the subscapularis muscle (number 3 in the image). A better image can be found in “An Illustrated Atlas of the Skeletal Muscles” by Bowden (2015) which we cannot publish for copyright reasons.

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" 38th British Ed. Churchill Livingstone 1995
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015

Image modified from the original by Henry VanDyke Carter, MD. Public domain