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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Abdominal aorta
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UPDATED: The abdominal aorta is the fourth, last, and most distal portion of the aorta. It begins when the descending aorta passes through the aortic hiatus of the respiratory diaphragm, just about the level of the 11th or 12th thoracic vertebra. It ends inferiorly at the bifurcation of the aorta, anterior to the lower portion of the body of the 4th lumbar vertebra where the abdominal aorta is continuous with the right and left common iliac arteries.

The abdominal aorta gives off a number of paired (bilateral) and unpaired (single) arterial branches. The paired branches are:

Inferior phrenic arteries: provide blood supply to the respiratory diaphragm
Renal arteries: Provide blood supply to the kidneys
Gonadal arteries: Depending on the gender, they are called testicular or ovarian arteries, providing blood supply to the gonads
Lumbar arteries: There are four pairs of lumbar arteries, which pass posteriorly around the vertebral bodies and provide supply to the spine and the back.
Suprarenal arteries: These are several minute arteries that provide blood supply to the suprarenal glands. The suprarenal (adrenal) glands also receive several minute arteries that arise from the renal arteries and the inferior phrenic arteries.

The unpaired arterial branches of the abdominal aorta are: 

• Celiac trunk: Provides blood supply to the stomach, spleen, liver, and duodenum
• Superior mesenteric artery: Provides blood supply to duodenum, jejunum, ileum, and the right side of the colon
• Inferior mesenteric artery: Provides blood supply to the left side of the colon, and superior aspect of the rectum
• Middle sacral artery: This is the only branch of the aorta that arises from its posterior aspect, it descends providing blood supply to the sacrum and fifth lumbar vertebra

Clinically, the abdominal aorta is divided by the origin of the renal arteries into a suprarenal and an infrarenal segment. This division is important for the surgical treatment of abdominal aortic aneurysms (AAA). To see a AAA, click here.

The suprarenal segment is bound laterally by the crura of the respiratory diaphragm. and its inferior boundary is the superior aspect of the highest renal artery (usually the left renal artery). It has branches that are critical for the blood supply of most of the digestive tract, the celiac trunk and the superior mesenteric artery, plus the inferior phrenic arteries and the suprarenal arteries. 

The infrarenal segment includes the renal arteries, the inferior mesenteric artery, gonadal arteries, lumbar arteries, and the middle sacral artery.

Image property of:CAA.Inc.Artist:Victoria G. Ratcliffe