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Azygos vein
 
 
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The azygos vein is a vein running up the right side of the thoracic vertebral column
Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
. It can also provide an alternate path for blood to the superior vena cava
Superior vena cava

The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....
.

Structure
The azygos vein transports deoxygenated blood from the posterior walls of the thorax
Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs....
 and abdomen
Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity....
 into the superior vena cava
Superior vena cava

The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....
 vein. The anatomy of this blood vessel
Blood vessel

The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
 can be quite variable. In some rare variations for example, it also drains thoracic veins, bronchial veins and even gonadal veins.






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Encyclopedia


The azygos vein is a vein running up the right side of the thoracic vertebral column
Vertebral column

In human anatomy, the vertebral column is a column of 24 vertebrae, the sacrum, intervertebral discs, and the coccyx situated in the dorsum aspect of the torso, separated by spinal discs....
. It can also provide an alternate path for blood to the superior vena cava
Superior vena cava

The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....
.

Structure


The azygos vein transports deoxygenated blood from the posterior walls of the thorax
Thorax

The thorax is a division of an animal's body that lies between the head and the abdomen.In mammals, the thorax is the region of the body formed by the sternum, the thoracic vertebrae and the ribs....
 and abdomen
Abdomen

In vertebrates such as mammals the abdomen constitutes the part of the body between the thorax and pelvis. The region enclosed by the abdomen is termed the abdominal cavity....
 into the superior vena cava
Superior vena cava

The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....
 vein. The anatomy of this blood vessel
Blood vessel

The blood vessels are the part of the circulatory system that transport blood throughout the body. There are three major types of blood vessels: the artery, which carry the blood away from the heart, the capillary, which enable the actual exchange of water and chemicals between the blood and the tissues; and the veins, which carry blood from...
 can be quite variable. In some rare variations for example, it also drains thoracic veins, bronchial veins and even gonadal veins. The vein is so named because it has no symmetrically equivalent vein
Vein

In the circulatory system, veins are blood vessels that carry blood toward the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary vein and umbilical veins, both of which carry oxygenated blood....
 on the left side of the body.

It is formed by the union of the ascending lumbar veins with the right subcostal vein
Subcostal vein

The subcostal vein is a vein in the human body that runs along the bottom of the twelfth rib. It has the same essential qualities as the posterior intercostal veins, except that it cannot be considered intercostal because it is not between two ribs....
s at the level of the 12th thoracic vertebra, ascending in the posterior mediastinum
Mediastinum

The mediastinum is a non-delineated group of structures in the thorax , surrounded by loose connective tissue. It is the central compartment of the thoracic cavity....
, and arching over the right main bronchus
Right main bronchus

The right main bronchus is a bronchus of the respiratory system. It is wider, shorter, and more vertical in direction than the Left main bronchus....
 at the root of the right lung
Lung

The lung is the essential respiration organ in air-breathing animals, including most tetrapods, a few fish and a few snails. In mammals and the more complex life forms, the two lungs are located in the chest on either side of the heart....
 to join the superior vena cava. This "arch of the azygos vein" (arcus venae azygou) is an important anatomic landmark. As a rare anatomical variation, the arch can be displaced laterally, thereby creating a pleural septum separating an azygos lobe
Azygos lobe

In human anatomy, an azygos lobe is a rare congenital variation of the upper lobe of the right human lung. Embryology, it arises from an anomalous Anatomical terms of location course of the azygos vein in a pleural septum within the upper lobe....
 from the upper lobe of the right lung.

Its tributaries, apart from its main tributary, the hemiazygos vein, are the bronchial veins, pericardial veins, and posterior right intercostal veins. It communicates with the vertebral venous plexuses
Vertebral venous plexuses

Vertebral venous plexuses can refer to:* External vertebral venous plexuses* Internal vertebral venous plexuses...
.

Azygos venous system


The azygos system of veins is considered to be the azygos vein, along with its left-sided counterparts, the hemiazygos vein
Hemiazygos vein

The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column....
 and the accessory hemiazygos vein
Accessory hemiazygos vein

The accessory hemiazygos vein is a vein on the left side of the vertebral column that generally drains the fifth through eighth intercostal spaces on the left side of the body....
. Together, they form an anastomosis
Anastomosis

An anastomosis is a network of streams that both branch out and reconnect, such as blood vessels or leaf veins. The term is used in medicine, biology, mycology and geology....
 between the superior vena cava
Superior vena cava

The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....
 to the inferior vena cava
Inferior vena cava

The inferior vena cava is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....
.

It can be noted that the azygos system of veins exists because the superior vena cava
Superior vena cava

The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....
 and the inferior vena cava
Inferior vena cava

The inferior vena cava is the large vein that carries de-oxygenated blood from the lower half of the body into the right atrium of the heart....
 are not continuous. While the aorta travels downward (continuously) through the mediastinum, supplying blood to the intercostal spaces, the vena cava does not exist at the level of the heart. Thus, the azygos venous system makes up for this deficiency of the venae cavae.

Etymology

The Greek root zyg refers to a pair. 'A-' means not. Thus, azygos means unpaired. The azygos vein is unpaired in that there is only one in the body, mostly on the right side. While there is the hemiazygos vein
Hemiazygos vein

The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column....
 and its accessory on the left side of the body, they are considered tributaries of the azygos vein rather than its left-side equivalent.

Additional images


See also

  • Hemiazygos vein
    Hemiazygos vein

    The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column....
  • Posterior intercostal veins
    Posterior intercostal veins

    The posterior intercostal veins are veins that drain the intercostal spaces posteriorly. They run with their corresponding posterior intercostal artery on the underside of the rib, the vein superior to the artery....
  • Superior vena cava
    Superior vena cava

    The superior vena cava is a large, yet short vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium....


External links

- "Right side of the mediastinum
Mediastinum

The mediastinum is a non-delineated group of structures in the thorax , surrounded by loose connective tissue. It is the central compartment of the thoracic cavity....
."