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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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Serratus anterior (magnus)

The serratus anterior or serratus magnus is a is a wide, thin muscle sheet situated on the posterolateral aspect of the thorax and extends between the ribs and the scapula. It is formed by well-defined separate muscular digitations that originate in the external surface and superior aspect of the first superior eight (or nine) ribs. These originating fibers also arise from the fasciae covering the intercostal muscles. This is especially true for the first or most superior digitation which arises from the first and second rib and the intervening external intercostal fascia.

These digitations cover the lateral aspect of the thorax, pass deep to the scapula and converge to insert on the deep aspect of the medial border of the scapula. Some of its fibers may even hug the medial border of the scapula and insert on its anterior aspect. The first digitation is inserted into a triangular area on the ventral surface of the medial scapular angle. The next two digitations spread out to form a triangular sheet, the base of which is directed posteriorly and is inserted into nearly the whole length of the ventral surface of the vertebral border. The lower five or six digitations converge to form a fan-shaped mass, the apex of which inserts into a triangular impression on the ventral surface of the inferior scapular angle. The lower four slips of the serratus anterior interdigitate with the superior five muscular slips of the external oblique muscle.

Serratus magnus muscle - Image modified from the original by Henry VanDyke Carter, MD. Public domain
Serratus magnus muscle.
Click on the image for a larger depiction 
This muscle receives its nerve supply from the long thoracic nerve, (ventral rami of C5-C7), arising from the roots of C5, C6, and C7 (sometimes absent) of the brachial plexus

The word “serratus” is derivates from the Latin word [serro] meaning “saw”. Serratus means “serrated” referring to the multiple tooth-like anterior digitations of the muscle. The plural form for "serratus" is " serrati". The Latin term “magnus” means “great”, “large”, or “mighty”. It points to the fact that this is the largest of three muscles that carry the same name “serratus”. The other two are the serratus posterior superior and the serratus posterior inferior.

Note: The image shown in this article is from “Gray’s Anatomy” by Henry Gray (1918) which is in the public domain. It depicts the serratus anterior in situ and shows the scapula retracted posteriorly.  The scapula is covered on its internal aspect by the subscapularis muscle (number 3 in the image). A better image can be found in “An Illustrated Atlas of the Skeletal Muscles” by Bowden (2015) which we cannot publish for copyright reasons.

Sources:
1. “Gray’s Anatomy” Henry Gray, 1918
2. "Tratado de Anatomia Humana" Testut et Latarjet 8th Ed. 1931 Salvat Editores, Spain
3. "Gray's Anatomy" 38th British Ed. Churchill Livingstone 1995
4. “An Illustrated Atlas of the Skeletal Muscles” Bowden, B. 4th Ed. Morton Publishing. 2015

Image modified from the original by Henry VanDyke Carter, MD. Public domain