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

William S. Halsted, MD

William S. Halsted, MD
(1852 – 1922)

American anatomist, teacher, and surgeon, William Stewart Halsted was born in New York City, USA to a wealthy family of English origin. His father was involved in charitable work and Governor and trustee to a city hospital. Not a brilliant student initially, Halsted took an undergraduate in Liberal Arts in Yale, CT., after which he entered the Medical College of Physicians at the Columbia College, where he excelled.

As a second-year medical student Halsted applied and obtained a position in surgery at a local hospital. In here he learned about Lister’s antiseptic technique and became an adamant proponent of it to reduce infection. In 1877 Halsted obtained his MD. After a short time as House Physician at the New York Hospital, Halsted traveled to Europe to further his education studying for two years at the Universities of Vienna, Leipzig, and W?rzburg.

Besides being at the forefront of surgical and antiseptic techniques (introducing the use of rubber gloves in surgery), Halsted was extremely concerned with the way medical students were taught in the US. He pioneered bedside clinical round discussions with the medical students after two years of basic sciences studies. Halsted developed the idea of a patient chart; he also developed the residency program for medical students in use today.

Halsted is probably the most influential researcher and surgeon at the turn of the century. He dedicated time to the study of intestinal anastomoses and the use of silk as a suture material. His experimental work in 1887 proved that the inclusion of the submucosa layer in an anastomosis was mandatory, as well that a single layered anastomosis was enough to attain closure. Perhaps Halsted’s most important contribution was the application and use of the scientific method to surgical questions. Halsted’s principles, also known as  "Halsted's Rules of Surgery", set the standards used today in surgical suturing and surgical stapling.

He also pioneered the development and surgical techniques for radical mastectomy as a treatment for breast cancer.

As a side effect of this studied in anesthesia and the use of cocaine for anesthesia, Halsted became addicted to this substance, a problem that followed him through the years. Without impairing his capacity as a researcher and a surgeon, Halsted eventually recovered. He died in Baltimore in 1922 as a complication to surgery.

Sources:
1. Dubay, A. D., & Franz, G. M. (2003). Acute Wound Healing: The Biology of Acute Wound Failure. Surg Clin NA, 83, 463-481.
2. Halsted, W. S. (1887). Circular Suture of the Intestine - An Experimental Study. Am J Med Sci, 436-461.
3. “William Stewart Halsted: his life and contributions to surgery” Osborne, P. Lancet Oncol 2007; 8: 256–65
4. “William Stewart Halsted: Surgical pioneer” Burress, P Endoc Today (2010), 8: (2) 22
5. “William Stewart Halsted (1852–1922) Neurological stamp” Haas, LF J Neurol Neurosurg Psych 2000;69:641
Original image courtesy of "Images from the History of Medicine" at  www.nih.gov


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AV node as depicted by Sunao Tawara
Figure 1: AV node as depicted by Sunao Tawara

The atrioventricular (AV) node is a critical component of the conduction system of the heart, serving as the only (normal) electrical connection between the atria and the ventricles. By delaying atrioventricular transmission by 1/10th of a second, the AV node allows the heart to work as a pump.

The AV node is situated in the inferior portion of the interatrial septum. It was discovered in 1906 by Sunao Tawara, who identified it as a discrete small structure located at the atrioventricular junction and demonstrated continuity of the AV node with the His–Purkinje system (see image 1).

The AV node is a located in the “Triangle of Koch” (see note), a region bound by the tendon of Todaro, the septal leaflet of the tricuspid valve, and the ostium of the coronary sinus (see image 2). Its blood supply is by way of the AV node artery, a branch of the right coronary artery (RCA) that arises usually at the crux cordis, the point of division of the RCA into the posterior descending artery and posterolateral artery.

Triangle of Koch, location of the AV node

Image 2: SVC: Superior vena cava, RPA: Right pulmonary artery, RSPV: Right superior pulmonary vein, RIPV: Right inferior pulmonary vein, IVC: Inferior vena cava, RAA: Right atrial appendage, FO: Foramen ovale, TV: Septal leaflet of the tricuspid valve. The yellow line shows the location of the "Tendon of Todaro". The complete triangle is the triangle of Koch.  

The ventricles are isolated from the atria by connective tissue that forms an electrical barrier between. This barrier is sometimes called the “skeleton of the heart” a misnomer that does not explain the reason for its presence. If there was no barrier, the atria and ventricles would all contract at the same time and the pumping action of the heart would not exist.

The only place where the electrical impulse can pass from the atria to the ventricles is through the AV node. Because of the specialized cardiomyocytes that form the node, the transmission of the impulse is delayed by one tenth of a second, enough that the ventricles will contract after the atria contract, causing blood flow through the heart.

Note: The "triangle of Koch" is eponymically named after Walter Eduard Carl Koch (1880 - 1962) a German physician, anatomist, and pathologist.

Sources and References:
1. Markowitz, MM; Lerman BL. A contemporary view of atrioventricular nodal physiology. J Interv Card Electrophysiol. 2018 Aug;52(3):271-279.
2. Efimov IR, Nikolski VP, Rothenberg F, Greener ID, Li J, Dobrzynski H, Boyett M. Structure-function relationship in the AV junction. Anat Rec A Discov Mol Cell Evol Biol. 2004 Oct;280(2):952-65.
3.Fumarulo I, Salerno ENM, De Prisco A, Ravenna SE, Grimaldi MC, Burzotta F, Aspromonte N. Atrioventricular Node Dysfunction in Heart Failure: New Horizons from Pathophysiology to Therapeutic Perspectives. J Cardiovasc Dev Dis. 2025 Aug 15;12(8):310.
4. Anderson RH, Sánchez-Quintana D, Nevado-Medina J, Spicer DE, Tretter JT, Lamers WH, Hu Z, Cook AC, Sternick EB, Katritsis DG. The Anatomy of the Atrioventricular Node. J of Cardiovasc Development and Disease. 2025; 12(7):245.
5. Tawara, S.  Das Reizleitungenssystem des Säugetierherzens : eine anatomisch-histologische Studie über das Atrioventrikularbündel und die Purkinjeschen Fäden 1906 J Fischer pub. courtesy of archive.org
6. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
7. Anderson, Robert H. MD; Becker, Anton E. MD. "Slide Atlas of Cardiac Anatomy" 10 volumes London: Gower Medical Publishing, 1985. (out of print)