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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Triangle of Calot 
Image modified from the original
(Singh and Ohri, 2006

The [triangle of Calot], also known as the “cystohepatic triangle” is a triangular region found within the lesser omentum connecting the duodenum, stomach, and liver. It is an area bound superiorly by the inferior surface of the liver, laterally by the cystic duct and the medial border of the gallbladder, and medially by the common hepatic duct.

The surgical importance of this area is for a cholecystectomy. It is within this area that the surgeon will usually find the cystic artery, a critical structure that needs to be ligated in this procedure.  I stress the term “usually” as the hepatobiliary tree is one of the areas in the human body that has the most anatomical variations. In fact, the anatomy in this region is considered to be “normal” only in 64% of the cases. The cystic artery may not be found in the triangle of Calot therefore careful dissection and identification of the structures is needed in every surgery.

The above description of the triangle of Calot is what some refer to as the “modern triangle of Calot”, as the original triangle described by Dr. Jean-Francois Calot (1861 – 1944) is different.

Calot’s original description of this triangle is: “Le triangle n’est pas exactement équilatéral, mais plutôt isocéle, les deux cotés supérieur et inférieur, représente par l’artére et le conduit cystique, étant seuls égaux, et un peu plus longs que la partie du canal hépatique qui entre dans la constitution du triangle’’ , which can be translated as: “ The triangle is not exactly equilateral, but rather an isosceles triangle. The superior and inferior sides, represented by the cystic artery and cystic duct, are equal and a little longer than the part of the hepatic duct, which enters into the formation of the triangle. (Abdalla, 2013).

In the accompanying image Calot’s original triangle is shown by horizontal blue lines while the modern version of the triangle of Calot is shown with vertical red lines.

Sources:
1. “Calot's triangle” Abdalla S, Pierre S, Ellis H. Clin Anat. 2013 May;26 (4):493-501
2. “Anatomic landmarks: their usefulness in safe laparoscopic cholecystectomy” Singh, K; Ohri, A. Surg Endosc (2006) 20: 1754–1758
3. “Surgical Anatomy” Deaver, J P. Blakiston's Son & Co. Philadelphia, 1901
4. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
Image modified from the original (Singh and Ohri, 2006. Pastel sketch by Dr. E. Miranda