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Medical Terminology Daily (MTD) is a blog sponsored by Clinical Anatomy Associates, Inc. as a service to the medical community, medical students, and the medical industry. We will post a workweek daily medical or surgical term, its 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

Antoine Louis
(1723–1792)

French surgeon, anatomist, and physiologist. Following his medical studies and a long career as a physiologist, Antoine Louis was named Permanent Secretary of the Royal French Academy of Surgery. His other titles were those of Professor of the Royal Academy, Consultant Surgeon of the Armies of the King, member of the Royal Society of Sciences of Montpellier, Inspector of the Royal Military Hospitals, and Doctor in Law of the University of Paris. As a member of these academies Louis was instrumental in the design and construction of the guillotine. Initially called the "Louisette", this device was later named after another French physician in the same committee, Dr. Joseph-Ignace Guillotin.

Antoine Louis' name is better know to history as the eponymic origin of the "sternal angle" also know as the "Angle of Louis" and synonymously (probably by misspelling or translation) the "angle of Lewis", and "angle of Ludwig". This anatomical landmark is extremely important as it serves as a superficial landmark for important anatomical occurrences (click here).

As a point of controversy, there are some that contest the history of this eponym adjudicating it to Pierre Charles Alexander Louis (1787-1872), another French physician dedicated to the study of tuberculosis.

Sources:
1. Srickland, N; Strickland A Angle of Louis, More Than Meets the Eye. MedTalks:
2. Ramana, R. K., Sanagala, T. and Lichtenberg, R. (2006), A New Angle on the Angle of Louis. Congestive Heart Failure, 12: 197–199
3
. "The origin of Medical Terms" Skinner, HA; 1970


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Artery

UPDATED: The term [artery] evolved from two Greek words. The first one is [αέρα], meaning "air", and the second one is [terein], a verb meaning "to keep" or "to maintain"1. [Artery] therefore means "to maintain or to keep air", which is furthest from what we know today! The reason is that initial observations on these structures happened in bodies after combat, or gladiators who had exsanguinated because of their wounds. The arteries were empty (full of air) or contained a mix of blood and air. Arteries were considered a type of windipe. In fact, the original anatomical term for trachea was that of [tracheartery], which means "the rough artery". We have learned since then the true function of the arteries, so the name was shortened to "trachea".

The modern definition of an artery is "a structure that takes blood away from the heart". The amount of oxygen within the vessel has no bearing on the definition; there are arteries that carry oxygenated blood and arteries that carry deoxygenated blood.

 The structure of an arterial wall. Courtesy Blausen.com

Histologically, an artery is composed of three layers. The external layer is called the "adventitia" or "tunica externa". It is composed mostly of connective tissue. The middle layer is called the "tunica media" and is composed by a varying number of elastic fibers and smooth muscle fibers arranged as shown in the image. The inner layer is called the "tunica intima". The inner portion of the tunica intima is called the endothelium.

Arteries that are closer to the heart have more elastic fibers in their tunica media. As we move further away from the heart arteries become smaller and increase the number of smooth muscle fibers. This is what histologists describe "elastic arteries" and "muscular arteries". The smallest muscular arteries are called "arterioles". Large arteries have their own blood supply, called the "vasa vasorum".

Sources:
1.
"The ancient Hellenic and Hippocratic origins of head and brain terminology" Panourias IG, Stranjalis G, Stavrinou L, Sakas DE. Clin Anat 2012 Jul;25(5):548-581
2. Image: "Blausen Gallery 2014" 
- Wikiversity Journal of Medicine. DOI:10.15347/wjm/2014.010. ISSN 20018762. Licensed under Creative Commons Attribution 3.0 via Wikimedia Commons - Original image