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 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

The [sphincter of Oddi]  is a complex system of smooth muscles that controls flow of bile and pancreatic juice into the duodenum. Although known by its eponym, this structure has the anatomical name of "sphincter of the hepatopancreatic ampulla". Although described previously by others, it was Ruggero Oddi (1864-1913) who described not only its structure, but also its function.

The hepatopancreatic ampulla or "ampulla of Vater" is a dilation found at the conjunction and end of the common bile duct and pancreatic duct. The presence of the hepatopancreatic ampulla creates a nipple-like elevation of the duodenal mucosa called the "duodenal papilla".

The sphincter of Oddi has several components:

The duodenal muscular layer parts to allow passage of the complex formed by the hepatopancreatic ampulla and the sphincter of Oddi, creating a window called the "choledochal window". Longitudinal fibers from the duodenal muscularis externa pass and join to the sphincter of Oddi.

This is a root term of Greek origin. In both presentations [-chol-] or [-chole-] it means "bile" or "gall". The English word "gall" is of Anglosaxon origin and means "bile", referring to its yellowish-green color. The word [bile] is of Latin origin, from [bilis].

These root terms are used in many medical words, such as:

• cholecystitis: [cyst] means "sac" or "bladder", [itis] means "inflammation" or "infection". Gallbladder inflammation
• cholecystectomy: [cyst] means "sac" or "bladder", [ectomy] means "removal". Gallbladder removal
• cholangiogram: [angi] means "vessel", [(o)gram] means "examination". Examination of a bile vessel
• choledocholithiasis: Condition of stones in the bile duct. Click on the link for more information
• cholera: The suffix [-era] is "flow" or "discharge". The term refers to the constant vomiting of bile in patients afflicted with this disease. This term has been heatedly discussed and this is but one of the theories as to the etymology of the word.

In the early days of physiology, yellow bile was considered one of the "four humors" that made up human personality, temperament, and health. A person with an excess of yellow bile would be considered bad tempered, angry, or "choleric". Observe how the root term [chole] also is found in the word "choleric".

Sources:
1. "The Language of Medicine" John H. Dirckx Pub: Harper & Row 1976
2. "Medical Meanings" Haubrich, William S. Am Coll Phys Philadelphia 1997
3. "The origin of Medical Terms" Skinner, AH, 1970

Although the circular muscle of the sphincter of Oddi had already been described by Glisson in 1681, Oddi was the one who did a complete anatomical and physiological study of this structure uncovering the fact that it was indeed a sphincter. He continued his studies on the hepatobiliary sphincter until 1894, when he moved to Congo and later back to Belgium. 

Because of his inclination towards methaphysical studies, Oddi started experimenting with drugs on himself and became addicted.

Original imagecourtesy of National Library of Medicine.

Sources:
1. "Ruggero Ferdinando Antonio Guiseppe Vincenzo Oddi" Lukas, M, et al. World J Surg (2007) 31:2260–2265
2. "Ruggero Oddi; To commemorate the centennial of his original article--"Di unaspeciale disposizione a sfintere allo sbocco del coledoco" Ono, K; Hada, R. Jap J Surg, VOL. 18, No. 4 pp. 373-375, 1988
3. "Ruggero Oddi: 120 years after the description of the eponymous sphincter: A story to be remembered" Capodicasa, E. J Gastroent Hepat 23 (2008) 1200–1203
4. "Oddi: The Paradox of the Man and the Sphincter" Modlin, IM; Ahlman, H. Arch Surg 129 (1994) May 550-557