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

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

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Vermiform appendix

The word [vermis] is Latin and means "worm". The term [vermiform appendix] means "the worm-shaped appendage", and refers to a worm-like appendage that is related to the cecum, a segment of the right colon.

This structure was first described by Jacobo Berengario da Carpi in 1524, and it was Andreas Vesalius who first described it as an appendix, and suggested it looked like a worm. It has been called the [vermix] and the [cecal appendix]

The vermiform appendix1 has the same four layers found in most of the abdominal digestive tract and is attached to the cecum at the point where the three tenia coli (libera, mesenterica, and omentalis) meet. The length of the vermiform appendix is variable. On average about 2.5 to 3 inches, it can be as long as 10 inches in length, with one recorded case of a 13 inch appendix!2

Terminal ileum, cecum, and vermiform appendix (www.bartleby.com)Original image courtesy of www.Bartleby.com

The location of the vermiform appendix is also subject to anatomical variation, being found in a retrocecal position in 65% of the cases. For more information on this organ's anatomical variations, click here.

The vermiform appendix is an intraperitoneal structure, as it has a peritoneal extension called the mesoappendix. Within the mesoappendix are the appendiceal arteries and veins. The appendiceal artery is usually a branch of the ileocolic artery.

1. It is not proper to call this structure the "appendix", as there are many appendices in the human body.
2. Personal note: The longest vermiform appendix I have personally seen was 8 inches (20.3 cm) in length, retrocolic, and the tip of the organ was actually retrohepatic!.  Dr. Miranda.