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The pisiform bone is one of the four bones that comprise the proximal row of the carpus or carpal bones that form the wrist. It is the smallest of the carpal bones, is spheroidal in shape, and presents with only one articular surface (see image).

Its name originates from the Latin [pisum], meaning "pea". It is also known as "os pisiforme" or "lentiform bone", because some feel it is shaped like a lentil.

The pisiform bone articulates posteriorly with the triquetrum, and has on its anterior (volar) surface attachments to the transverse carpal ligament, and to the Abductor Digiti Quinti, and Flexor Carpi Ulnaris muscles.

The accompanying image shows the anterior (volar) surface of the wrist.

Image modified from the original: "3D Human Anatomy: Regional Edition DVD-ROM." Courtesy of Primal Pictures

This is a Latin word meaning a trench, a ditch, or an excavation. It arises from the Latine term [fodere] meaning "to dig". The plural form for "fossa" is "fossae".

There are many fossae listed in human anatomy, here are some of them:

• fossa scaphoides: found in the pinna
• fossa ovalis: found in the wall of the right atrium
• fossa triangularis: found in the pinna
• ischioanal fossa: a triangular fossa found in the perineum, inferior to the pelvic diaphragm and superior to the urogenital diaphragm, etc.

The prefix [pre-] has its origin in the Latin preposition [prae] meaning "anterior", "in front of", or "before". 

Applications of this prefix include:

• precordial: anterior to the heart, as in "precordial pain"
• preoperative: before the operation
• preperitoneal: anterior to the peritoneum, referring to the region found outside and anterior to the peritoneal sac, an area containing fat, and important for preperitoneal laparoscopic surgery
• presystolic: before systole
• preaortic: anterior to the aorta

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The right coronary artery usually bifurcates in an area of the posterior aspect of the heart known as the "crux cordis" giving origin to two terminal branches: the posterior interventricular artery (anatomical term) and the posterolateral artery. The posterior interventricular artery is better know to clinicians as the "posterior descending artery" or PDA.

The PDA descends towards the apex cordis where it ends. It gives off several small ventricular branches, but its most important branches are the septal perforators. These branches dive deep and provide blood supply to the posterior 1/3rd of the interventricular septum.

The AV node artery, which provides blood supply to the AV node (a component of the conduction system of the heart) may arise from the PDA instead of arising from the right coronary artery.

The PDA may present with a number of anatomical variations, including:

• arising from the circumflex artery (and absence of the posterolateral artery)
• arising from the first septal perforator of the anterior interventricular artery
• arising from the second diagonal artery
• arising from anterior interventricular artery
• being double, with one PDA arising from the circumflex artery, and another from the right coronary artery, etc.

Image property of: CAA, Inc. Photographer: E. Klein

This article is part of the series "A Moment in History" where we honor those who have contributed to the growth of medical knowledge in the areas of anatomy, medicine, surgery, and medical research.

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Sunao Tawara, M.D. (1873 - 1952) Sunao Tawara was born in the prefecture of Ooita, Kyushu, Japan. Adopted by an uncle (and physician), Tawara studied English and German, and went on to the University of Tokyo medical school, where he graduated an MD in 1901.

In 1903 he traveled to Marburg, Germany, where he started working with Dr. Karl Albert Ludwig Aschoff (1866-1942), a noted pathologist. Tawara’s work led him to the discovery of what today we call the “atrioventricular node” (AV node) and the connections of the AV node and the Bundle of His (the right and left bundle branch). His work with Aschoff led to the eponym of “node of Aschoff-Tawara” for the AV node. Tawara’s work also led to the understanding of the function of the Purkinje fibers. Tawara gave the entire system the name “Reitzleitungssytem” or the “conduction system” of the heart.

In 1906 Dr. Tawara published his discoveries in a German-language article entitled “The Conduction System of the Mammalian Heart — An Anatomicopathological Study on the Atrioventricular Bundle and the Purkinje Fibers”. The same year he returned to Japan and in 1908 became Professor of Pathology at the University of Kyushu until his retirement in 1933.

Sources:
1. "Sunao Tawara" Suma, K. Clin Cardiol (1991) 14; 442-443
2. "Sunao Tawara, A Cardiac Pathophysiologist" Loukas, M. et al Clinical Anatomy 21:2–4 (2008)
3. "Sunao Tawara: A Father of Modern Cardiology" Suma, K. J Pacing Clin Electrophysiol (2001) 24:1; 88- 96

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The [circumflex artery]  (CFX) is one of the two branches of the left coronary artery, the other one being the left anterior descending artery (LAD), also known as the anterior interventricular artery.

The prefix [circum-] means "around", while the root term [-flex-] means "to bend". This describes quite well the circumflex artery, which "bends around" the obtuse margin of the heart passing from the anterior surface to the posterior surface of the heart.

The circumflex artery lies deep to the epicardium in the subepicardial fatty layer. It gives off several branches, including small left atrial branches and one or two obtuse marginal arteries (OM1 and OM2)that provide blood supply to the left ventricle in its obtuse margin and posterior ventricular region, as well as a portion of the anterior papillary muscle related to the mitral valve.

There can be interesting anatomical variations in the coronary arteries of the heart. For a detail on these anatomical variations, click here. Heart and coronary artery anatomy is one of the many lecture topics presented by CAA, Inc.

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