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

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.

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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Dr. Willem Einthoven

This article is part of the series "A Moment in History" where we honor those who have contributed to the growth of medical knowledge in the areas of anatomy, medicine, surgery, and medical research.To search all the articles in this series, click here.
Dr. Willem Einthoven (1860 - 1927). Einthoven was Dutch, born on 1860 in the city of Semarang in the island of Java. His father was a physician working for the Dutch military. He started his medical studies at the University of Utrecht, Holland. Having developed an interest in ophthalmology and physiology, he developed his medicine doctorate thesis on stereoscopic color vision.

In 1885 Einthoven became a Professor of Physiology at the University of Leiden. Having seen a demonstration of Augustus Waller’s “electrogram” (a device that recorded minute deviations on a mercury column when electrically stimulated) in 1887, he improved it by creating the “string galvanometer”. In 1901 Einthoven published his first recordings of what he called “elektrokardiogramm” (EKG).

The initial device was bulky, heavy, and required the patient to sit with both arms and the left leg in separate buckers of salt water, but it did record the electrical activity of the heart (Click here for an image of one of the first electrocardiographs). Eventually the device was commercialized and history was made. It was Einthoven who used the letter P,Q,R,S, and T in electrocardiography.

In 1924, Willem Einthoven was awarded the Nobel Prize in Physiology.

Dr. Willem EinthovenOriginal imagecourtesy of "Images from the History of Medicine" at www.nih.gov.

1. "Willem Einthoven (1860-1927): father of electrocardiography". Merritt, C. Tan. SY. Singapore Med J 53:(1) 17
2. "Willem Einthoven (1860-1927)" Davies, M; Hollman, A. Heart. 1997 October; 78(4): 324
3. "Willem Einthoven: The development of the human electrocardiogram" Cajavilcaa, C.,Varonb, J.Resuscitation 76:3 2008; 325–328


The word [vermis] is Latin and means "worm". 

The vermis is the name given by Galen of Pergamon (129AD - 200AD) to the median lobe of the cerebellum, since when seen from the superior aspect, this cerebellar lobe looks like a multisegmented worm. See accompanying image, or click for a larger depiction. 

When seen in a median section, the cerebellar vermis looks like a multilobulated leaf with the fourth ventricle of the brain at its base. It is composed of several smaller lobules: Lingula, central, culmen, clivus, tuber vermis, pyramid, uvula, and nodular lobes.

Median section image link courtesy of UCLA Radiology

Superior view of the cerebellum (modified from bartleby.com)Modified from the original image. Courtesy of www.Bartleby.com

Anatomical variations (3)

"The Chirurgeon must knowe the Anatomie". Thus states Thomas Vicary (1460 -1561) on the knowledge of Anatomy. He continues: "...for all authors write against those surgeons who work in a man's body not knowing the Anatomie"1. There is no doubt that knowledge must include the awareness of the possibility of anatomical variations.  Some anatomical variations, like the "Corona Mortis" can be critical, and in some surgical cases, be the cause for exsanguination!

It is interesting that several medical schools are reducing the total number of hours working on, or moving away from cadaver disection in first year medical school and using computer simulations instead. No computer simulation will give the medical student the detail, variations, and feel of the tissues as actual hands-on experience. I am sure no one wants a surgeon whose first view of the internal aspect of a human body is a living patient...on the surgical table. 

It is a fact that "Nothing in the human body is really colored... or labeled" or as someone else said "nothing looks exactly like the anatomy book", unless it is photography, and then each photo is taken after hours of laboring to "Netterize" the organ or area that one is trying to detail. Nothing gives the future professional the exact idea of what to expect in the future patient than the hours and hours of laborious work in the anatomy laboratory.

Coronary artery arising from the pulmonary trunk (Brooks, 1886)
The same is true with anatomical variations, one "standard" digital cadaver,even with built-in anatomical variations does not give the student the sense of awe and discovery when an anatomical variation is found, interpreted, and analyzed with a group of peers, contributing to the learning process and the formation of future health care professionals.When questioning what is normal or abnormal, Dr. Elizabeth Murray says it most elegantly: "The cadaver is always right"

The image depicts a case of a coronary artery arising from the pulmonary trunk

1. "The Chirurgeon must knowe the Anatomie" R. Shane Tubbs Clin Anat 26:417 (2013)
2. "Two cases of an abnormal coronary artery of the heart arising from the pulmonary artery"Brooks, H; J. Anat. Physiol. 20:26-29, 1886 (anatomyatlases.org)



Anatomical variations (2)

"No anatomical structure has the moral obligation to be where they are supposed to be"

Not only may an anatomical structure be absent, such as in the case of renal aplasia or agenesis, or in the case of a non-existent circumflex coronary artery, but sometimes extra structures can be found. Such is the case where a kidney can present two or even three ureters, all functional. Double inferior vena cavae, cervical ribs, lumbar ribs, the list goes on and on!

Muscles can be added to this list, again, with absence of a muscle, or with new and completely unexpected attachments. An example of this is the presence of a continuation of the rectus abdominis muscle into the chest region, a variation called a sternalis muscle.

The accompanying image shows the sternalis muscle in one of the "muscle plates" of De Humani Corporis Fabrica Libri Septem, published in 1543 by Andreas Vesalius. This image was criticized by showing a muscle that does not exist, although Vesalius clearly stated in the text of his book that this was an anatomical variation that he had seen.

For many decades surgeons had to operate and "see what they could find". There were the days of the exploratory laparotomy. After the discovery of the application of X-rays by Wilhem Konrad Roentgen (1845 - 1923) and the incredible advances in imaging techniques including CT-scan, MRI, PET, etc, the surgeon is now not usually surprised by anatomical variations.

Sternalis muscle (Andreas Vesalius 1543)
There are areas in the body that have an high rate of anatomical variation, such as the hepatobiliary region, which includes the "Triangle of Calot". In this area, the standard anatomy is found only in 64% of the cases! In the rest, expect the unexpected. Lahey (1948) states "...the fact that cholecystectomy is a dangerous operation. It is dangerous unless one realizes.... that anomalous anatomy is very common". Today the dangers are less, because of better visualization and technology, but anatomical variations are still there.

Another area where anatomical variations are extremely important is the heart's coronary circulation. Anatomical variations can cause different cardiac dominance. Normal anatomy states that there are two coronary arteries, yet, up to five separate coronary arteries arising directly from the ascending aorta have been described! There is one variation where the left coronary arises from the right coronary artery, effectively having only one artery arise from the aorta and being in charge of all the arterial supply to the heart. What happens if this single artery stenoses? Bear in mind that this is not an "anomalous" vessel, it is just an anatomical variation.

1. Lahey DH, discussing the paper "Partial Hepatectomy with Intrahepatic Cholangiojejunostomy" by Wilson H, and Gillespie CE, Ann Surg. 1949 June; 129(6): 756–765
2. "Renal aplasia is the predominant cause of congenital solitary kidneys" Hiraoka, M et al Kidney Int. 2002 May;61(5):1840-4.

This article is the second in a series of three; Click here for the first article

Anatomical variations (1)

"The only constant in anatomy is variation". This dictum is incredibly powerful and true. Even the so-called "anatomical constants" are subject to it.

One common misconception is that "we are all the same". This could not be further from the truth. Every body is different from every else's body. Anatomical variations range from the minimal to the incredible. One of the most interesting anatomical variations is the one called "situs inversus". In this case the individual is a mirror image of a human. The apex of the heart points to the right side of the body; the duodenum circles to the right, the liver "hangs" from the left side of the respiratory diaphragm, etc. This particular anatomical variation presents in different degrees and can sometimes coexist with some cardiovascular congenital abnormalities.

Third supernumerary kidney. (modified from Dixon, 1911
Of course there are minor anatomical variations that have no effect on daily life at all and are only discovered by accident, or upon autopsy or dissection. One of the most complete resources on this topic is the Illustrated Encyclopedia of Human Anatomic Variations. An excerpt from this site states: "It is clear that textbook writers and teachers over the centuries, even until today, fail to understand or to transmit to their students the crucial concept that anatomical and physiological diversity and variation is a canon of living organisms. This failure leads to the belief that textbooks are conveying immutable facts with only few anomalous exceptions".

Shown here is an extremely rare case of a third kidney. Dixon (1911) describes in his research paper that as of that date, only 10 cases were known, of these only eight were recorded, with 87% of them found on the left side of the body. Click on the image for a larger depiction.

Source and primary image: "Supernumerary kidney: The occurrence of three kidneys in an adult male subject" Dixon, A.F. J. Anat. Physiol. 45:117-121, 1911.



The prefix [para-] has a Greek origin and means "beside" or "alongside". Today we add the meaning of "parallel to".

We see the daily application of this prefix  in words such as [paramedic], [parajournalism], [paralogism], and [paranormal].

Medical applications of the term include:

paraesternal: alongside the sternum, such as the internal thoracic vessels
paramedian: alongside the median plane
parasagittal: parallel to a sagittal plane (synomym with paramedian)
paraumbilical: alongside the umbilicus, such as paraumbilical visceral extrusion in a gastroschisis
parathyroid glands: glans that are found besides the thyroid gland, etc.