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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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Esophageal hiatus

UPDATED: The esophageal hiatus is one of the seven hiatuses found in the respiratory diaphragm allowing passage of structures between the thorax and abdomen. As it name implies, the esophageal hiatus is the passageway for the esophagus. It also allows passage of the anterior and posterior vagus nerves, (CN X).

The hiatus is bound by two muscular crura, both of which arise from the right tendinous aortic crus. Since the intraabdominal pressure is higher than the intrathoracic pressure, there is a series of structures at the phrenoesophagogastric junction to close the esophageal hiatus.

The infradiaphragmatic parietal peritoneum reflects off the diaphragm towards the stomach to form its serosa layer (visceral peritoneum). At the same time the infradiaphragmatic fascia, also known as the  endoabdominopelvic fascia, splits into two components or limbs. These are the superior and inferior phrenoesophageal ligaments or phrenoesophageal membranes. (the root [-phren-] means "diaphragm"). These phrenoesophageal ligaments create a disc-like plug between the abdomen and the thorax. This "plug" is reinforced by a circular infradiaphragmatic fat pad. The phrenoesophageal ligaments are reinforced on their thoracic aspect by the endothoracic fascia.

Esophageal hiatus

Images property of: CAA.Inc. Artist: Dr. E. Miranda

The lower esophagus has a dilation (evident in the image) called the "esophageal ampulla", in relation to this dilation the circular muscle layer of the esophagus slightly thickens creating the so-called "lower esophageal sphincter". This area is not a true anatomical sphincter, but rather is a functional sphincter. 

The esophagogastric mucosal junction shows a marked transition in the shape of a wavy line. This is called the Z-line or the ora serrata. Extensions of the gastric mucosa and submucosa inferior to the ora serrata create a valve-like flap called the "gastroesophageal flap valve". When viewing this mucosal flap through and endoscope, it looks corrugated and flower-like, hence it is also called the "rosette". 

The congenital or pathological dilation of the esophageal hiatus can predispose to esophageal hiatus hernia.