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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

Thomas Willis, MD
Thomas Willis
(1621-1675)

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.

Sources:

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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Pelvic diaphragm

The pelvic diaphragm is one of the four diaphragms in the human body (do you know the other three?) and it represents the lower boundary of the abdominopelvic cavity. This thin and  transversely oriented structure is formed from anterior to posterior by the puboccygeus, the iliococcygeus, and the coccygeus muscles.

The first two anterior muscles overlap, the pubococcygeus muscle being superior to the iliococcygeus muscle. Both of them attach laterally to a thickening of the obturator internus fascia that covers the obturator internus muscle. This thickening is known as the arcus tendineus levator ani (ATLA in the image). Because of the relation of the medial fibers of the puboccygeus muscle to the anal canal (puborectalis muscle), and what happens when these muscles contract, these two anterior muscles are known by one common name, the "levator ani" muscle. Click on the picture for a larger image.

Pelvic diaphragm, superior view
The posterior component of the pelvic diaphragm is the coccygeus muscle, which is found lying on the internal aspect of the sacrospinous ligament.
Image property of: CAA.Inc.Artist: D.M. Klein
Word suggested and edited by: Dr. Sanford S. Osher, MTD Contributor