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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Lumbar vertebra

The lumbar region of the spine is composed by five lumbar vertebrae. Although sharing characteristics common to all vertebrae, a lumbar vertebra can be differentiated by the following:

• The vertebral body is large, tall, and when viewed from superior, the vertebral body has a longer transverse diameter and a shorter anteroposterior diameter. Most anatomists describe the vertebral body as being “kidney-shaped”. The massiveness of the vertebral body is due to the larger weight that each consecutive vertebra has to bear in the lumbar region. Because of this, lumbar vertebrae have larger anular epiphyses, and the vertebral body is hourglass-shaped with a “waist”.  As with other vertebrae, the body of a lumbar vertebra has vertebral endplates, nutritional foramina, and in its posterior aspect they present with basivertebral foramina.

• The pedicles in the lumbar vertebrae are larger, course in a mostly anteroposterior direction, and have a oval cross-section where the superoinferior diameter is longer and the transverse diameter is shorter. This is important for transpedicular procedures for vertebroplasty or kyphoplasty.

• The transverse processes are also larger than other vertebrae. Of interest are the facts that the transverse process of the third lumbar vertebra is the longest of all lumbar vertebrae and that the transverse process of the fifth lumbar vertebra courses superolaterally at an angle of  almost 45 degrees because of the presence of the strong iliolumbar ligament. The lumbar transverse processes have a small tubercle called the mammillary process.

• The lumbar spinous processes are large and have a square shape.

Again, because of the larger weight bearing capacity of the lumbar vertebrae, they have strong ligaments and their zygapophyseal joints and articular facets tend to be oriented with their surfaces in a transverse plane. This has two consequences: The rotational mobility of the whole lumbovertebral region is limited and they tend not to have anteroposterior displacement.

Lumbar vertebra - lateral view
Lumbar vertebra - Lateral view.

Lumbar vertebra - inferior view
Lumbar vertebra - Inferior view.

Image property of CAA.Inc. Photographer:D.M. Klein.