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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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Mediastinum

UPDATED: The mediastinum is the median region of the thorax, usually described as the "space"1 between the lungs. This region is divided into a superior and inferior mediastinum by a plane that pases through the sternal angle or Angle of Louis.

The inferior mediastinum is itself divided into three separate regions by the pericardial sac. The region anterior to the pericardial sac is the "anterior mediastinum", the region posterior to the pericardial sac is the "posterior mediastinum", and the region containing and including the pericardial sac is the "middle mediastinum". Thus described the mediastinum comprises four regions as follows:

Superior mediastinum:  It contains the aortic arch, the brachiocephalic trunk, the thoracic segments of the left common carotid and the left subclavian arteries, the brachiocephalic veins, a portion of the superior vena cava, the vagus nerve, phrenic nerve, and left recurrent laryngeal nerve, trachea, esophagus, thoracic duct and the remains of the thymus gland

Anterior mediastinum: A narrow space, more developed on the left side, anterior to the pericardial sac and contains some lymph nodes and connective tissue

Middle mediastinum: The largest mediastinal region, it contains the pericardial sac, the heart, the bifurcation of the trachea, the inferior vena cava, and the cardiac end of the great vessels

Mediastinum (www.en.wikipedia.org)

Images courtesy of Wikipedia.org

• Posterior mediastinum: Contains the descending aorta, the azygos and hemiazygos veins, the esophagus, and thoracic duct.

1. Personally, I do not use the description of the mediastinum as a "the space beween the lungs", as it conjures the image of literal "open spaces" around or between the organs. The fact is that the mediastinum is tightly packed with no spaces between the organs. This is why I prefer the definition of the mediastinum as an "area" or "region" between the lungs. Dr. Miranda.