Azygos vein
Encyclopedia
The azygos vein is a vein running up the right side of the thoracic vertebral column
. It can also provide an alternate path for blood to the right atrium
by allowing the blood to flow between the venae cavae when one vena cava is blocked.
and abdomen
into the superior vena cava
vein. The anatomy of this blood vessel
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
on the left side of the body.
It is formed by the union of the ascending lumbar vein
s with the right subcostal vein
s at the level of the 12th thoracic vertebra, ascending in the posterior mediastinum
, and arching over the right main bronchus
posteriorly at the root of the right lung
to join the superior vena cava. This "arch of the azygos vein" (arcus venae azygos) 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
from the upper lobe of the right lung.
A major tributary is the hemiazygos vein
, a similar structure on the opposite side of the vertebral column. Other tributaries include the bronchial veins, pericardial veins, and posterior right intercostal veins. It communicates with the vertebral venous plexuses
.
and the accessory hemiazygos vein
.
and its accessory on the left side of the body, they are considered tributaries of the azygos vein rather than its left-side equivalent.
This terminology is only accurate in some species, such as the human, dog and cat. Ruminants (such as sheep and cows) have paired azygos veins
."
Vertebral column
In human anatomy, the vertebral column is a column usually consisting of 24 articulating vertebrae, and 9 fused vertebrae in the sacrum and the coccyx. It is situated in the dorsal aspect of the torso, separated by intervertebral discs...
. It can also provide an alternate path for blood to the right atrium
Right atrium
The right atrium is one of four chambers in the hearts of mammals and archosaurs...
by allowing the blood to flow between the venae cavae when one vena cava is blocked.
Structure
The azygos vein transports deoxygenated blood from the posterior walls of the thoraxThorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
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 truly superior, a large diameter, 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 transports blood throughout the body. There are three major types of blood vessels: the arteries, which carry the blood away from the heart; the capillaries, which enable the actual exchange of water and chemicals between the blood and...
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 towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are the pulmonary and umbilical veins, both of which carry oxygenated blood to the heart...
on the left side of the body.
It is formed by the union of the ascending lumbar vein
Ascending lumbar vein
The ascending lumbar vein is a vein that runs up through the lumbar region on the side of the vertebral column.-Structure:The ascending lumbar vein is a paired structure...
s 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...
posteriorly at the root of the right lung
Lung
The lung is the essential respiration organ in many 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 near the backbone on either side of the heart...
to join the superior vena cava. This "arch of the azygos vein" (arcus venae azygos) 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 lung. Embryologically, it arises from an anomalous lateral course of the azygos vein in a pleural septum within the upper lobe...
from the upper lobe of the right lung.
A major tributary 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.-Structure:...
, a similar structure on the opposite side of the vertebral column. Other tributaries include 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 veinHemiazygos vein
The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.-Structure:...
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.-Structure:...
.
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 veinHemiazygos vein
The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.-Structure:...
and its accessory on the left side of the body, they are considered tributaries of the azygos vein rather than its left-side equivalent.
This terminology is only accurate in some species, such as the human, dog and cat. Ruminants (such as sheep and cows) have paired azygos veins
See also
- Hemiazygos veinHemiazygos veinThe hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column.-Structure:...
- Posterior intercostal veinsPosterior intercostal veinsThe 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. Each vein also gives off a dorsal branch that drains blood from the muscles of the...
- Superior vena cavaSuperior vena cavaThe superior vena cava is truly superior, a large diameter, yet short, vein that carries deoxygenated blood from the upper half of the body to the heart's right atrium...
- Chronic cerebrospinal venous insufficiencyChronic cerebrospinal venous insufficiencyChronic cerebrospinal venous insufficiency is a term developed by Italian researcher Paolo Zamboni in 2008 to describe compromised flow of blood in the veins draining the central nervous system...
External links
- "Right side of the mediastinumMediastinum
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...
."