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.

Click on the link below to subscribe to the MTD newsletter. If you think an article could be interesting to somebody else, click on the mail link at the top of each article to forward it. 

You are welcome to submit questions and suggestions using our "Contact Us" form. The information on this blog follows the terms on our "Privacy and Security Statement"  and cannot be construed as medical guidance or instructions for treatment. 

Click here to subscribe to the Medical Terminology Daily Newsletter

fbbuttons sm

We have 174 guests and no members online

A Moment in History

Thomas Willis, MD
Thomas Willis

An English physician and anatomist, Willis was born on his parents' farm in Great Bedwyn, Wiltshire, where his father held the stewardship of the Manor. He was a kinsman of the Willys baronets of Fen Ditton, Cambridgeshire. He graduated M.A. from Christ Church, Oxford in 1642. In the Civil War years he was a royalist, and was dispossessed of the family farm at North Hinksey by Parliamentary forces. In the 1640's Willis was one of the royal physicians to Charles I of England. He obtained his medical degree in 1646.

Thomas Willis might well be one of the greatest physicians of the 17th century.He is one of the founders of the Royal Society of London. He is remembered by his many publications, especially "Cerebri Anatome: Cui accessit Nervorum Descriptio et Usu", where he describes the arterial anastomoses at the base of the brain. This work is also the first detailed description of the vasculature of the brain. Willis described nine cranial nerves.

He is considered as the father of Neurology as a discipline. He used the term "neurology" for the first time in 1664. He described several neurological conditions

The Arterial Circle of Willis is a famous eponymous structure found at the base of the brain. It represents an anastomotic roundabout that connects the right and left sides as well as the carotid and vertebral arterial territories that supply the brain. Named after Thomas Willis, this structure was known well before him, but it was Willis who described its function.  If you click on the image or here, you will be redirected to a detailed description of this structure.


1. "The legendary contributions of Thomas Willis (1621-1675): the arterial circle and beyond" Rengachary SS et al J Neurosurg. 2008 Oct;109(4):765-75
2. "Thomas Willis, a pioneer in translational research in anatomy (on the 350th anniversary of Cerebri anatome)" Arraez-AybarJournal of Anatomy, 03/2015, Volume 226, Issue 3
3. " The naming of the cranial nerves: A historical review" Davis, M Clinical Anatomy, 01/2014, Volume 27, Issue 1
4. "Observations on the history of the circle of Willis". Meyer A, Hieros, R.Med Hist 6:119–130, 1962

"Clinical Anatomy Associates, Inc., and the contributors of "Medical Terminology Daily" wish to thank all individuals who donate their bodies and tissues for the advancement of education and research”.

Click here for more information

Rare & Collectible Books at AbeBooks.com 



The rectum is the most distal segment of the large intestine. 

The word [rectum] arises from the Latin [rectus] and means "straight", such as its use in the name "rectus abdominis" for the "straight muscle of the abdomen".

It seems a misnomer, as the rectum of the human species is actually "S" shaped, as seen in the accompanying image. The reason for this discrepancy is that the rectum was named by Galen of Pergamon (129AD - 200 AD) who himself studied this structure in animals such as sheep and goats. In these animals the rectum is indeed straight, and since contradicting Galen was not acceptable (see Michael Servetus), the name has survived until this day. Even Andreas Vesalius has in his 1953 "Fabrica" a depiction of a straight rectum in the human! Click on the bar beneath the image to see Vesalius' image of the rectum.

The proximal end of the rectum is not clearly discernible from the sigmoidorectal region, from here the rectum has an "S" shape, measures approximately six to seven inches in length (15 - 17 cm), and it ends distally at the junction of the rectum with the  pelvic diaphragm. It is at this point that the anal canal begins.

1. Sigmoid colon 2. Rectum 3. Anus 4. Inferior rectal valve 5. Middle rectal valve 6. Superior rectal valveLarge Intestine - Vesalius 1543
The rectum is characterized by three transverse rectal folds, one on the right side, and two on the left side. These folds are know as the "rectal valves" or the "valves of Houston". The middle rectal fold is known to European anatomists as the "valve of  Kohlrausch" Their function in maintaining fecal material in place as well as their function in defecation is still under study. The rectal valves also have a high level of anatomical variation and may not be present at all.

Image source: "Tratado de Anatomia Humana" Testut et Latarjet 8 Ed. 1931 Salvat Editores, Spain
Recommended reading: "Transverse Folds of Rectum: Anatomic Study and Clinical Implications" Shafik, A, et al. Clin Anat 14: 196-203 (2001).

-card- / -cordi-

These two root terms mean "heart".

The first one, [-card-] arises from the Greek [kardium]  and can be seen in medical words such as: cardiac, echocardiogram, cineangiocardiogram, cardioplegia, myocardial infarction, etc.

The second one [-cordi-] arises from the Latin [cordis] and can be seen in words such as: precordial pain, cordial, commotio cordis, etc. 

As a point of interest, the original Greek spelling of [kardium]  was used by Nobel prize winner Dr. Willem Einthoven (1860 - 1927) when he invented the electrocardiograph and the electrocardiogram. The German term is [elektrokardiogramm] and the German abbreviation for the procedure is EKG. Since we use the term in Engish, [electrocardiogram] we use the abbreviation ECG. Both are correct, although if you are speaking English, ECG should be used.

HeartImage property of:CAA.Inc.Artist:Victoria G. Ratcliffe

Collateral circulation

The term "collateral circulation" is generally used to denote a situation where small blood channels dilate and provide blood supply when a pathology creates a stricture and diminishes blood flow (ischemia).

Although the above is correct, the term is also applicable to a normal, non-pathological situation most common in the human body. Please refer to the accompanying image for the following explanation. If needed, click on the image for a larger depiction. In the image, the arrows represent direction of flow.

Most organs or organ segments receive blood supply from more than one source of blood supply. In some cases, like the stomach, there are up to four arteries that provide blood supply to the organ: the right and left gastric arteries, and the right and left gastroepiploic arteries.

Collateral circulation. The arrows indicate direction of arterial blood flow. The dashed lines delimitate vascular territoriesImages property of:CAA.Inc. Artist: Dr. E. Miranda
In other cases, like the small intestine shown in the image, blood arrives to the organ arising from several arteries (A, B, and C) that themselves arise from a parent structure. Because of hydrodynamics, the vascular territories of each artery (represented by dashed lines) tend not to overlap. If for any reason there is stenosisor blockage in any of these arteries (A,B, or C) blood will flow immediately through an alternate route and the organ will not suffer ischemia or necrosis

This is extremely important, as these collateral channels maintain blood supply to areas that may be affected by bending, such as the elbow and knee, which have a rich collateral network. Most of the organs in the body, with some exceptions (brain, heart), have collateral circulation.

Collateral circulation is extremely important for surgery, as surgeons can safely remove parts of organs without affecting the blood supply to the organ. This is also true for all gastrointestinal anastomoses.


Histology is the scientific branch that studies tissues.

The root term [-hist-] is used to mean "tissues", but how the term came to be used is somewhat convoluted. It arises from the Greek [histos], which indicates the mast of a ship, it then was used to denote a Greek weaver's loom central mast (where the fabric is woven horizontally), and then it was used to indicate that which was woven [histios], the fabric, or the "tissues".  The suffix [-ology] also has Greek origin from [logos] meaning a "book", a "treatise" or "to study". 

The concept of the body being formed by different tissues was pioneered by Marie-Francois Xavier Bichat (1771-1802) who called them "membranes" Bichat is considered to be the "father of Histology". The image shows a histological slide of cardiac muscle. Click on the image for a larger depiction.

Cardiac muscle (Dr. S. Girod, A. Becker)Original image by S. Girod and A. Becker, courtesy of Wikipedia. 


The root term [-spondyl-] arises from the Greek [spondylos] meaning "vertebra", and the suffix [-osis] means "condition", but with the connotation of "many". The word [spondylosis] means " condition of many vertebrae". This does not add much to the use of this word as an indicator of a pathology, but it does indicate that there is excess bone in a vertebral pathology.

Spondylosis is an osteoarthritic degeneration of the vertebrae and the spine characterized by abnormal bony growths  on the vertebrae that can impinge on nerves and other structures causing pain and mobility problems. The definition of spondylosis also includes degenerative changes in the intervertebral discs.

The abnormal growth of portions of the vertebral body, usually forms "bone spurs", also referred to as "spondylophytes". The accompanying image shows a lumbar vertebra with spondylophytes. Click on the image for a larger depiction.

Spondylophytes on a lumbar vertebraImage property of: CAA.Inc. Photographer: David M. Klein

Rudolf Nissen, MD

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. Rudolf Nissen (1896 - 1981).  Dr Nissen’s life is extraordinary. Born in the city of Neisse, Germany in 1896, he was the son of a local surgeon. He studied medicine in the Universities of Munich, Marburg, and Breslau. He was the pupil of the famous pathologist Albert Aschoff (discoverer of the heart’s AV node, along with Sunao Tawara).

Nissen became a professor of surgery in Berlin, and in 1933 moved to Turkey where he was placed in charge of the Department of Surgery of the University of Istanbul. In 1939 he moved to the US, first to the Massachusetts General Hospital and later to the Jewish Hospital in Brooklyn, New York. After becoming a US citizen, he moved again in 1952 to Basel, Switzerland as Chief of the Department of Surgery, where he retired in 1967. He died in 1981.

His contributions to surgery are innumerable. He wrote over 30 books and 450 journal articles. Known for the development in 1956 of what is today known as the “Nissen fundoplication” for esophageal hiatus hernia surgery, Nissen also worked with his assistant, Dr. Mario Rossetti to develop the “floppy Nissen fundoplication”, also known as the “Nissen-Rossetti procedure”. This would be enough to honor this man, still, he (with Sauerbruch) performed the first lung lobectomy and the first pneumonectomy (called then a total pneumonectomy). In 1949 he performed the first esophagectomy with a gastroesophagostomy for lower esophageal cancer.

Dr. Rudolph NissenOriginal imagecourtesy of Universit?t Basel.
His personal life is even more interesting. Drafted at 20, he fought in WWI and was wounded several times. In 1933, under the Nazi regime, he was ordered to fire all the Jewish-German assistants under his care. Being Jewish himself, he was told that he would keep his job, Nissen could not take this. He resigned his position and moved out of Germany.

Another little known fact is that he operated on Albert Einstein in 1948. He operated on Einstein because of intestinal cysts. Having found a developing abdominal aortic aneurysm, he reinforced it with cellophane, undoubtedly giving his patient a few extra years to live. Einstein died in 1955.

As a personal side note, our good friend Dr. Aaron Ruhalter scrubbed in with Dr. Nissen while serving as a surgical resident at the Brooklyn Jewish Hospital!

1. “Rudolf Nissen: The man behind the fundoplication” Schein et al. Surgery 1999;125:347-53
2. “Rudolf Nissen (1896–1981)-Perspective” Liebermann-Meffert, D. J Gastrointest Surg (2010) 14 (Suppl 1):S58–S61
3. “The Life of Rudolf Nissen: Advancing Surgery Through Science and Principle” Fults, DW; Taussky, P. World J Surg (2011) 35:1402–1408
4. “Total Pneumonectomy” Nissen, R. Ann Thorac Surg 1980; 29:390-394
5. “Historical Development of Pulmonary Surgery” Nissen, R. Am J Surg 80: Jan 1955 9- 15