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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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The term [trapezoid] is formed by the root term [-trapez-] which arises from the Latin [trapezius] and itself a derivative of the Greek [τραπέζι] meaning "a small table", referring to an irregular four-sided shape. It also has the suffix [-oid] meaning "similar to". The word then means "similar to a four-sided table".
The Trapezoid bone is one of the four bones that comprise the distal row of the carpus or carpal bones that form the wrist. This bone is also known as the "lesser multiangular bone" because of its many angles, surfaces and sharp edges. The Latin name for this bone is os multtangulus minus.
The following text is from Gray's anatomy with annotations in []: "The superior surface, quadrilateral, smooth, and slightly concave, articulates with the navicular [scaphoid bone]. The inferior surface articulates with the proximal end of the second metacarpal bone; it is convex from side to side, concave from before backward and subdivided by an elevated ridge into two unequal facets. The dorsal [posterior] and volar [anterior] surfaces are rough for the attachment of ligaments, the former being the larger of the two. The lateral surface,convex and smooth, articulates with the greater multangular [trapezium bone]. The medial surface is concave and smooth in front, for articulation with the capitate [bone]; rough behind, for the attachment of an interosseous ligament."
The accompanying image shows the anterior (volar) surface of the wrist.
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The root term [-carp-] arises from the Greek word [καρπό] meaning “wrist”. The adjectival form is [carpal] meaning “pertaining to the wrist”.
The carpus is a complex region between the hand and the forearm. It is composed by 8 bones arranged in two rows, as well as ligaments and joints that maintain the bones together and in position.
The proximal row is formed from lateral to medial by the following bones: scaphoid, lunate, triquetrum, and pisiform.
The distal row is formed from lateral to medial by the following bones: trapezium, trapezoid, capitate, and hamate.
The accompanying image shows the anterior (volar) surface of the wrist. Click on the image for a larger picture. More information on the wrist and its joints will be published soon.
Image modified from the original: "3D Human Anatomy: Regional Edition DVD-ROM." Courtesy of Primal Pictures
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The term [capillary] is derived from the Latin word [capillus], which refers to a hair of the head.
Capillaries are the smallest components of the cardiovascular system, microscopic vessels that are actually thinner than a hair. Most capillaries are shorter than 1mm in length and their diameter is so narrow that it allows for red blood cells to only pass single file through them (see accompanying video). This accounts for a slow passage of blood through the capillary allowing for exchange of gases and nutrients between the vessel and surrounding tissues.
Capillaries are formed by a single cell wall known as endothelium. In the video, you can see a capillary clearly at the center of the screen, the reverse of flow and movement at the end of the video is an artifact.
Thanks to Stephen Taylor for the use of his video on YouTube.
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UPDATED: The term [artery] evolved from two Greek words. The first one is [αέρα], meaning "air", and the second one is [terein], a verb meaning "to keep" or "to maintain"1. [Artery] therefore means "to maintain or to keep air", which is furthest from what we know today! The reason is that initial observations on these structures happened in bodies after combat, or gladiators who had exsanguinated because of their wounds. The arteries were empty (full of air) or contained a mix of blood and air. Arteries were considered a type of windipe. In fact, the original anatomical term for trachea was that of [tracheartery], which means "the rough artery". We have learned since then the true function of the arteries, so the name was shortened to "trachea".
The modern definition of an artery is "a structure that takes blood away from the heart". The amount of oxygen within the vessel has no bearing on the definition; there are arteries that carry oxygenated blood and arteries that carry deoxygenated blood.
Histologically, an artery is composed of three layers. The external layer is called the "adventitia" or "tunica externa". It is composed mostly of connective tissue. The middle layer is called the "tunica media" and is composed by a varying number of elastic fibers and smooth muscle fibers arranged as shown in the image. The inner layer is called the "tunica intima". The inner portion of the tunica intima is called the endothelium.
Arteries that are closer to the heart have more elastic fibers in their tunica media. As we move further away from the heart arteries become smaller and increase the number of smooth muscle fibers. This is what histologists describe "elastic arteries" and "muscular arteries". The smallest muscular arteries are called "arterioles". Large arteries have their own blood supply, called the "vasa vasorum".
Sources:
1. "The ancient Hellenic and Hippocratic origins of head and brain terminology" Panourias IG, Stranjalis G, Stavrinou L, Sakas DE. Clin Anat 2012 Jul;25(5):548-581
2. Image: "Blausen Gallery 2014" - Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. Licensed under Creative Commons Attribution 3.0 via Wikimedia Commons - Original image
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Although blood circulation is one constant circle of flow, it consists of two subsystems: pulmonary and systemic circulation mediated by the heart. Within the systemic circulation there are other subsystems: coronary, portal (hepatic), and renal.
Deoxygenated blood comes into the right atrium of the heart. The blood coming from the body does so by way of the superior vena cava and the inferior vena cava. The blood coming from the heart does so by way of the coronary sinus, the anterior coronary veins, and the venae cordis minimae. Thus, the right atrium receives the blood return from the whole body, including the heart.
From the right atrium, the deoxygenated blood passes through the tricuspid valve (one of the two atrioventricular valves) into the right ventricle. Upon contraction of the right ventricle (ventricular systole) blood is propelled through the pulmonary (sometimes called pulmonic) valve into the pulmonary trunk. The pulmonary trunk divides into a right and a left pulmonary artery, each of which enter a lung, thus starting pulmonary circulation.
Within the lung the arteries divide until they form a minute capillary meshwork around the alveolar sacs. At this point the deoxygenated blood discharges its CO2 and gains O2, becoming oxygenated blood which converges back towards the heart by way of pulmonary veins.
The oxygenated blood enters the left atrium by way of the four pulmonary veins. It passes into the left ventricle through the mitral valve (also known as the bicuspid valve), then it exits through the aortic valve and into the aorta. This starts systemic circulation.
The aorta and its branches provide oxygenated blood to all the body. Once the blood is deoxygenated, it comes back to the right atrium of the heart where the cycle starts again.
As a side note, all the vessels that enter or leave the heart are known as the great vessels. How many are the great vessels? For the answer, click here.
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William Harvey
This word derives from the Latin [circulus], meaning a “small circle”, or a “ring”. The act of walking or moving as in a circle in Latin is “circulare”.
In reference to the movement of the blood, the term was not known as the concept of blood flow in a closed circuit “as in a circle” was coined by William Harvey (1578 – 1609) (see image). Before Harvey, Michael Servetus (1511 - 1553) hinted at this concept, but never took it to its logical conclusion: that blood circulates.
In asking my students about this concept, few ever associate the term “circulation” with “circle” or a “closed circuit”.
Click here to read the description of the circulation of blood through the heart.
Original image courtesy of: nlm.nih.gov
