Another Pet Peeve: Misused Anatomical Directional Terminology

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A Moment in History

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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Details: Written by: Efrain A. Miranda, Ph.D.; Published: May 30, 2025; Created: May 30, 2025; Hits: 1770

Original Facebook image

For those who follow this blog or my articles on LinkedIn you know that I have several pet peeves regarding the misuse of medical and anatomical terminology. You can read some of these articles in the following links:

Recently, reading an article on Facebook, I realized that there are many people, some of them health care professionals, who use (and teach) anatomical directional terminology incorrectly. The post itself shows an image depicting directional terminology in humans.

The original image is shown here and if you hover your mouse on it you will see my concerns. If you click on it, you will see a larger depiction of these concerns.

1. Dorsal and Ventral and… 2. Caudal and Cranial

These four terms are used by many, referring to the human body in the anatomical position. The fact is that in the human anatomy, the proper terms to use are as follows:

1. Instead of ventral, the proper term to use is anterior.
2. Instead of dorsal, the proper term to use is posterior.
3. Instead of cranial, the proper term to use is superior.
4. Instead of caudal, the proper term to use is inferior.

Let’s look at the etymology behind the terms.

Ventral arises from the Latin [ventrum] and [venter] which means “abdomen” or “belly”. Some contend that the term means “towards the abdomen” and even say that the term is correct because the abdomen is the largest part of the anterior aspect of the body. In any case, never use the term “stomach” to mean abdomen (another pet peeve).

The term dorsal arises from the Latin [dorsum] which means “back”.

Click for a larger image

The term cranial arises from the Latin [cranium] meaning “skull”. Not mentioned in the image is the term “cephalad” which is Greek [κεφάλι] meaning “head”. The suffix [ad] means “toward”, so cephalad means “towards the head”.

Additional controversy is found with the term “caudal” or “caudad”. It originates from the Latin [cauda] which means “tail”. How can anyone say that the feet are “caudal” when the tail is the coccyx? Despite this, there are many who teach the term caudal and define it as “towards the feet”, even knowing the origin of the term.

The reason for these terms is that they are used in veterinary medicine and embryology. You see, in a quadruped, these four terms apply perfectly as you can see in this image.

The terms “cranial” and “caudal” are also used in embryology. Since the embryo is curved, we need terms that reflect this curvature, and since the upper and lower extremities have not yet developed, the tail is the “end” of the embryo! As for the terms “ventral” and “dorsal”, the image the follows is self-explanatory… the back of the embryo is almost all of it! See the following image:

Controversy also arises from the use of the term “dorsal” to refer to the superior aspect of the foot. It is just a consensus. The inferior aspect of the foot is referred a “plantar”, and “dorsal” was adopted to reflect this opposition.

Click for a larger image

In the comments to this Facebook article, C. Hartig mentioned “rostral”. The term [rostrum] is Latin and means “beak”. In Roman times the term was used to denote a speaker’s platform, as the dais was usually adorned with eagles that had a pointed beak. Through use, the term “rostrum” was used as “face” (some people have a very pointed nose).

In anatomy we use the term rostral as “face”. The term is used in neuroanatomy and refers to a plane that is transverse to the axis of the Central Nervous System. See the accompanying image. In the spinal cord, the terms “rostral” and “caudal” follows the transverse plane of the body. In the head, the axis of the brainstem changes and now an axial image of the brainstem is angled. In the cerebrum this changes again and now points anteriorly towards the face (or frontal lobe).

This leads to the misuse of the term “axial”. Yes, it can be used as “transverse plane, but only when referring to the body as a whole. This changes when we use the term “axial” referring to an organ or structure. An “axial” image of the heart is different from a “transverse image of the heart.

A word of caution. Because of the importance of embryology in neurogenesis of the nervous system, these embryological terms are used in adult neuroanatomy, Hence the terms "dorsal root ganglion", "ventral horn", ventral root", etc.

3. Sagittal Plane

The term “Axes of the CNS (Dr. Miranda, 1977)” arises from the Latin [sagitta], meaning “arrow”. An arrow would transfix someone from front to back. A sagittal plane is a vertical plane that divides the body into right and left portions. Since a plane has no width (geometrical definition) there are infinite sagittal planes. Only one divides the body into equal right and left portions. This is the midsagittal plane or median plane.

The image is correct in the sense that the median plane is one of many sagittal planes, but this representation forces many students to misuse the terms. If it is a median or midsagittal image, say so.

Disclaimer: I do not know the origin of the original image in the Facebook post, whether it is copyright-free or not. I used it because it has been posted publicly. All other images in this article are personal, copyright-free, or proper attribution have been posted as required by copyright law.

Sources:

1. "Tratado de Anatomia Humana" Testut et Latarjet 8 Ed. 1931 Salvat Editores, Spain
2. “The Origin of Medical Terms” Skinner HA 1970 Hafner Publishing Co.
3. "Medical Meanings, A Glossary of Word Origins" Haubrich, W.S. 1997. American College of Physicians, Philadelphia, PA.
4. "Elementos de Neuroanatomía" Fernandez, J.; Miranda, EA.
5. "Dorland's Illustrated Medical Dictionary" 28th Ed. W.B. Saunders. 1994
6. "Medical Terminology; Exercises in Etymology" Dunmore CW, Fleischer RM 2nd Ed. 1985
7. "Medical Meanings; A Glossary of Word Origins" Haubrich, WS. Am Coll Phys 1997
8. "Lexicon of Orthopædic Terminology" M. Diab. 1999. Amsterdam Hardwood Academic Publishers.
9. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995