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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Levator scapulæ muscle - Image modified from the original by Testut and Latarjet. Public domain
Levator scapulæ muscle

The levator scapulæ muscle (levator anguli scapulæ) is a triangular multipennate muscle which extends between the cervical spine and the scapula. This muscle is deep to the sternocleidomastoid and trapezius muscle.

It is formed by discrete muscular slips that originate from the first four transverse processes (C1-C4). It can have an extra slip from C5 (as shown in the side image).

These muscular slips pass posteroinferiorly, joining, and inserting in the superior scapular angle and the scapular medial border between the superior scapular angle and the medial origin of the scapular spine. It may attach to the scapular spine.

There are other anatomical variations including muscular slips that may extend to the occipital bone or mastoid process, to the trapezius, scalene, or serratus anterior magnus muscles, or to the first or second rib.

It receives nerve supply from the fourth and fifth cervical nerves and by a branch from the dorsal scapular nerve. The dorsal scapular nerve arises from the C5 root of the brachial plexus.

It receives its blood supply from the dorsal scapular artery.

The function of this muscle depends on which bony element is fixed, the scapula or the cervical spine. When the spine is fixed, the levator scapulae elevates the scapula and pulls the superior portion of the medial scapular border superomedially. When only one scapula is fixed, the head and neck flexes and rotates ipsilaterally while it extends the neck contralaterally.

Levator scapulæ muscle fibers - Image modified from the original by Arnold 1968
Levator scapulæ muscle fibers

The order and shape of the muscular slips is interesting, as the slip from the transverse process of the Atlas (C1) twists posteriorly and descends to insert as the most posterior and inferior fibers in the medial border of the scapula. The other slips follow a similar pattern, which is what allows this muscle to rotate the neck. This indicates that the fibers of the levator scapulae muscle are spiral and the fibers follow the contour of the neck. This makes (to my knowledge) the levator scapulae the only spiral muscle of the body. This is shown as "A" in the second side image; "B" represents the misconception on the direction of the fibers in this muscle.

Since it is a common sign of stress and bad posture to raise the shoulders, this muscle can spasm, causing neck pain and in some cases be a trigger for headaches.

The Levator scapulæ is one of the 17 muscles that attach to the scapula.

Note: The first side image shown in this article is from “Gray’s Anatomy” (1918) which is in the public domain. The second side image is from Arnold’s “Reconstructive Anatomy” (1968).

Note: Animated image below by Wikimedia Commons - Anatomography [CC BY-SA 2.1 jp (https://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)]

Anatomography [CC BY-SA 2.1 jp (https://creativecommons.org/licenses/by-sa/2.1/jp/deed.en)]

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918 2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
2. "Tratado de Anatomía 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
5. “Reconstructive Anatomy, A Method for the Study of Human Structure” Arnold, M. W.B. Saunders. 1968“Gray’s Anatomy” Henry Gray, 1918