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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Abdominal aorta

UPDATED: The abdominal aorta is the fourth, last, and most distal portion of the aorta. It begins when the descending aorta passes through the aortic hiatus of the respiratory diaphragm, just about the level of the 11th or 12th thoracic vertebra. It ends inferiorly at the bifurcation of the aorta, anterior to the lower portion of the body of the 4th lumbar vertebra where the abdominal aorta is continuous with the right and left common iliac arteries.

The abdominal aorta gives off a number of paired (bilateral) and unpaired (single) arterial branches. The paired branches are:

Inferior phrenic arteries: provide blood supply to the respiratory diaphragm
Renal arteries: Provide blood supply to the kidneys
Gonadal arteries: Depending on the gender, they are called testicular or ovarian arteries, providing blood supply to the gonads
Lumbar arteries: There are four pairs of lumbar arteries, which pass posteriorly around the vertebral bodies and provide supply to the spine and the back.
Suprarenal arteries: These are several minute arteries that provide blood supply to the suprarenal glands. The suprarenal (adrenal) glands also receive several minute arteries that arise from the renal arteries and the inferior phrenic arteries.

The unpaired arterial branches of the abdominal aorta are: 

• Celiac trunk: Provides blood supply to the stomach, spleen, liver, and duodenum
• Superior mesenteric artery: Provides blood supply to duodenum, jejunum, ileum, and the right side of the colon
• Inferior mesenteric artery: Provides blood supply to the left side of the colon, and superior aspect of the rectum
• Middle sacral artery: This is the only branch of the aorta that arises from its posterior aspect, it descends providing blood supply to the sacrum and fifth lumbar vertebra

Abdominal aorta</span></span> </span><span style=

Abdominal aorta- Anterior view. Click on the image for a larger version.

Clinically, the abdominal aorta is divided by the origin of the renal arteries into a suprarenal and an infrarenal segment. This division is important for the surgical treatment of abdominal aortic aneurysms (AAA). To see a AAA, click here.

The suprarenal segment is bound laterally by the crura of the respiratory diaphragm. and its inferior boundary is the superior aspect of the highest renal artery (usually the left renal artery). It has branches that are critical for the blood supply of most of the digestive tract, the celiac trunk and the superior mesenteric artery, plus the inferior phrenic arteries and the suprarenal arteries. 

The infrarenal segment includes the renal arteries, the inferior mesenteric artery, gonadal arteries, lumbar arteries, and the middle sacral artery.

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