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.

Abraham Vater

Abraham Vater (1684 - 1751) German anatomist and physician, Abraham Vater was the son of a distinguished physician and was born on the city of Wittenberg. He obtained a Doctorate in Philosophy (PhD) in 1706 and his medical degree in 1710 at the University of Leipzig. He became a professor “extraordinarius” of Anatomy and Botany in 1719, continuing his career in anatomy until he obtained the highest professorial degree at the University.

Click for a larger image

The word [epicardium] is composed by the prefix [epi-], meaning "outer" or "above"; the root term [-card-], meaning "heart"; and the suffix [-ium], meaning "layer" or "membrane". Thus, the word means "outer layer of the heart".

The epicardium is part of a larger structure called the pericardium, in fact, since the pericardium is in contact with a viscus (the heart), it can also be called "visceral pericardium". It must be noted that these two terms are synonyms: "epicardium" and "visceral pericardium".

The epicardium is a type of serosa composed of an outer layer formed by mesothelial cells and an inner layer formed by loose connective tissue containing varying amounts of fat. This inner layer known as the "subepicardial layer" (a misnomer) also contains elastic fibers.

The main arterial and venous components of the coronary circulation are found in the subepicardial layer. When performing a Coronary Artery Bypass Graft (CABG), a surgeon has to open the outer layer of the epicardium, and enter the subepicardial layer to perform the graft anastomosis. 

As a serosa, the epicardium is involved in the production and absorption of a clear fluid, the "pericardial fluid". This fluid acts as a lubricant for the pericardium, allowing for the effortless movement of the heart within the pericardial sac.

The suffix [-iasis] has an original Greek root (such as in [iatros] meaning "healer" or "hospital"). It later became a Latin root meaning "condition, pathology, or disease".

This suffix can be found in many medical terms such as:

• Choledocolithiasis - a condition of stones in the bile duct.
• Elephantiasis - A condiction where a body part grows unusually large, usually lower extremities and/ or scrotum
• Phthiriasis- A condition or infestarion with public or crab lice
• Helminthiasis- A bodily infestation with a type of parasitic worms called helminths (tapeworms)
• Cystolithiasis -  Bladder stones

Anterior view of the sphenoid bone

Both these root terms have their origin from the Greek [πτέρυγα] (ptéryga) and mean "wing".

In human anatomy the most common use of this root term is in the word [pterygoid]. Since the suffix [-oid] means "similar to", the word pterygoid means "similar to a wing", or "wing-like".

On the inferior aspect of the sphenoid bone (os sphenoidale) there are two very thin bat-wing-like bony appendages that are called the lateral and medial pterygoid plates. The medial pterygoid plate has a hook-like bony appendage called the hamulus (Latin: little hook).

Related to the pterygoid plates are the lateral and medial pterygoid muscles, both these muscles aid inthe process of mastication.

The root term [pter-] can be found in words such as [pterodactyl] meaning "winged finger", it refers to a phrehistoric winged animal; [pteranodon], and [pterosaurus].

Sources:
1 "Tratado de Anatomia Humana" Testut et Latarjet 8 Ed. 1931 Salvat Editores, Spain
2. "Anatomy of the Human Body" Henry Gray 1918. Philadelphia: Lea & Febiger
Image in the public domain modified by CAA, Inc. Original image courtesy of bartleby.com

Note: Google Translate includes the symbol (?). Clicking on it will allow you to hear the pronunciation of the word.

Click for a larger image

The sinuatrial node, is also known as the "sinoatrial node", "SA node" or by its eponym, the "node of Keith and Flack". It is the initial component of the conduction system of the heart.

It is a small nodule of cardiac muscle tissue, somewhat horseshoe-shaped that is found at the junction of the superior vena cava and the right atrium. Because of the inherent automaticity and rhythmical contractions of the SA node, it acts as the main pacemaker of the heart, being the base for normal heart beat, also known as "sinus rythm"

It receives blood supply from the SA node artery, usually the first or second branch that arises off the right coronary artery. The SA node artery is a long vessel that passes between the right atrium and the ascending aorta on its way to the SA node.

The SA node receives innervation from both sympathetic and parasympathetic nerves. The parasympathetic innervation is by way of the vagus nerve, the X^thcranial nerve. The sympathetic innervation is by way of the cardiac nerves, a plexus that has its origin in the ventral ramiof the first four thoracic spinal nerves (T1-T4).

The SA node was discovered in 1906 by Martin W.  Flack (1882-1931) and Arthur Keith (1866-1955). They named it originally the sinoauricular node.

Click on the image for a larger version. Image modified from the original: "3D Human Anatomy: Regional Edition DVD-ROM." Courtesy of Primal Pictures

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.

Wilhelm His Jr.

Wilhelm His Jr. (1863-1934). Also known as Wilhelm His the Younger, was born in Switzerland in the city of Basel. His father was a well-known and famous anatomist by the same name who worked at the University of Basel. Wilhelm His Jr. studied in several universities, including Leipzig, Strasbourg, Bern, and Geneva. He received his medical degree from the University of Leipzig in 1889.

Although not an anatomist, his 1893 single and most brilliant contribution to the eventual understanding of the conduction system of the heart was the discovery and description of a muscular bundle that connected the atrial septum with the ventricular septum. Until that moment it was known that no muscles crossed from the atria to the ventricles, leading anatomists and physiologists to wonder how does the heart contract.  

In his article His states "after long search I have succeeded in finding a muscle bundle which unites the auricular and ventricular septal walls, and which, up to now, has escaped observation because of incomplete exposure, for it is visible in its entire extent only when the septa are cut exactly in their longitudinal direction".

What is interesting is that His not only found the bundle that today honors his name, but he included in that description the atrioventricular node, the actual structure that crosses the atrioventricular connective tissue barrier known as the "skeleton of the heart". The AV node was later to be clearly identified and researched by Sunao Tawara (1873 - 1952).

Dr. His continued his research on gout and joint diseases. He became a German citizen and joined the German army as a consulting physician. He retired in 1932 and died in 1934.

Although Wilhelm His Jr. did not discover or described the esophagogastric angle, in 1906 JD Cunningham started calling this angle the "Angle of His" in honor of Wilhelm His Jr. This eponym has stayed with us until today.

Sources:
1. "Wilhelm His Jr." JAMA. 1964;187(6):453-454
2. "His, Jr., W.: The Activity of the Embryonic Human Heart and Its Significance for the Understanding of the Heart Movement in the Adult" Arb Med Klin Leipzig, pp 14-49, 1893; Bast, TH,Gardner, WD trans: J Hist Med 4:289-318, 1949
3. "Wilhelm His, Jr. and the Bundle of His" Bast, TH, Gardner, WD J Hist Med All Sci; 1949; 4, (2) 170 -187
4. Firkin BG (1996) Dictionary of medical eponyms.London: Parthenon Publishing Group, 181
Original image in the public domain, courtesy of the National Library of Medicine.