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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

Johann Gottfried Zinn

Johann Gottfried Zinn
(1727–1759)

Anatomist and botanist, Johann Gottfried Zinn was born on December 6, 1727 in the city of Ansbach, Germany. He started his medical studies in his native city, becoming later a student of Dr.  Albrecht von Hallers at the University of Göttingen, and received his MD in 1749.

He left for Berlin to continue his studies but came back shortly thereafter. He became a professor of anatomy at the University of Göttingen and in 1753 he also became the director of the botanical garden in the same city.

He is known for his anatomical treatise on the anatomy of the human eye: “Descriptio anatomica oculi humani iconibus illustrata”. Because of this, his name has become an eponym in the “Zonule of Zinn”, a ring of strands that forms a fibrous band connecting the ciliary body with the capsule of the lens of the eye. Zonule of Zinn is sometimes referred to as the suspensory ligaments of the lens, or the “ligament of Zinn”. His name is also attached to the anular ring tendon found in the posterior aspect of the eye, the "anular tendon of Zinn". This ring serves as attachment for all the extraocular muscles of the eye and the optic nerve passes through the center of the ring.

Carol Linné (Carolus Linneaus) named a genus of flowers in the family Asteraceae known vernacularly today as “Zinnia” in his honor. Hover your cursor over his portrait to see the flower.

The chapter on orbital anatomy of his anatomy book, taken from the second edition in 1780, has been translated and the first of three parts is published in an issue of “Strabismus”

His book "Catalogus Plantarum Horti Academici Et Agri" can be seen online here.

His life was short, dying at the early age of 32, but his name lives on in the name of a beautiful flower.

Sources:
1. “Johann Gottfried Zinn" Simonz, HJ Strabismus – 2004, Vol. 12, No. 2, p. 125 
2. "Anatomical Description of the Human Eye" Zinn, JG Strabismus, 13:45–52, 2005 
Images: Public Domain by Wikipedia Commons. 1. Own work I_am Jin, and H. Wilhem Dietz


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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.