Azygos vein
Vena azyga
- Latin synonym: Vena azygos
Definition
The azygos vein begins opposite the first or second lumbar vertebra, by a branch, the ascending lumbar vein; sometimes by a branch from the right renal vein, or from the inferior vena cava.
The azygos vein enters the thorax through the aortic hiatus in the diaphragm, and passes along the right side of the vertebral column to the fourth thoracic vertebra, where it arches (arch of azygos vein) forward over the root of the right lung, and ends in the superior vena cava, just before that vessel pierces the pericardium. In the aortic hiatus, it lies with the thoracic duct on the right side of the aorta; in the thorax it lies upon the intercostal arteries, on the right side of the aorta and thoracic duct, and is partly covered by pleura.
The azygos vein receives the right subcostal and intercostal veins, the upper three or four of these latter opening by a common stem, the highest superior intercostal vein. It receives the hemiazygos veins, several esophageal, mediastinal, and pericardial veins, and, near its termination, the right bronchial vein. A few imperfect valves are found in the azygos vein; but its tributaries are provided with complete valves.
The ethymology of azygos originates from the Greek word "Zyg" that means "paired" and prefix A that means "not".
References
This definition incorporates text from a public domain edition of Gray's Anatomy (20th U.S. edition of Gray's Anatomy of the Human Body, published in 1918 – from http://www.bartleby.com/107/).