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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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Snowman sign

The “snowman sign” is a particular image on a chest X-Ray image, which is seen in anomalous pulmonary venous drainage and coarctation of the aorta which causes a Total Anomalous Pulmonary Venous Return (TAPVR).

This abnormality occurs when the pulmonary veins fail to drain into the left atrium and instead form an aberrant connection with some others cardiovascular structures. Such abnormalities account for approximately 2% of cardiac malformations.

There are four types of TAPVR; type 1 is the most common (and the one that creates the snowman sign). In this case the pulmonary veins terminate at the supracardiac level, emptying into the right atrium by way of an anomalous pulmonary venous drainage into the superior vena cava (SVC), and the left brachiocephalic vein (by way of a vertical vein). The confluence of these veins dilates the right brachiocephalic vein, which appears as a dilated vessel on the right of the upper mediastinal edge. When seen in an AP Chest X-Ray, the TAPVAR type 1, resembles a snowman; the dilated vertical vein on the left, the right brachiocephalic vein superiorly, and the SVC on the right form the head of the snowman, the body is formed by the enlarged right atrium.

Article written by: Prof. Claudio R. Molina, MsC

Snowman sign
Snowman sign.
Click on the image for a larger depiction

Sources:
1. Emma C. Ferguson, Rajesh Krishnamurthy, and Sandra A. A. Oldham. (2007) Classic Imaging Signs of Congenital Cardiovascular Abnormalities. RadioGraphics 27:5, 1323-1334.
2. Somerville, J., & Grech, V. (2009). The chest x-ray in congenital heart disease 1. Total anomalous pulmonary venous drainage and coarctation of the aorta. Images in Paediatric Cardiology, 11(1), 7–9.