Hemiazygos vein
Encyclopedia
The hemiazygos vein is a vein running superiorly in the lower thoracic region, just to the left side of the vertebral column
.
, when taken together, essentially serve as the left-sided equivalent of the azygos vein
. That is, the azygos vein serves to drain most of the posterior intercostal veins
on the right side of the body, and the hemiazygos vein and the accessory hemiazygos vein drain most of the posterior intercostal veins on the left side of the body. Specifically, the hemiazygos vein mirrors the bottom part of the azygos vein.
The structure of the hemiazygos vein is often variable. It usually begins in the left ascending lumbar vein
or renal vein
, and passes upward through the left crus
of the diaphragm to enter the thorax
. It continues ascending on the left side of the vertebral column
, and around the level of the ninth thoracic vertebra, it passes rightward across the column, behind the aorta
, esophagus
, and thoracic duct
, to end in the azygos vein
.
The hemiazygos may or may not be continuous superiorly with the accessory hemiazygos vein
.
It receives the 9th, 10th, and 11th posterior intercostal veins
and the subcostal vein
of the left side, and some esophageal and mediastinal veins.
. Azygos means 'unpaired', and hemi means half. This vein mirrors the bottom half the azygos vein.
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...
.
Structure
The hemiazygos vein and the accessory hemiazygos veinAccessory 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:...
, when taken together, essentially serve as the left-sided equivalent of the azygos vein
Azygos vein
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.-Structure:...
. That is, the azygos vein serves to drain most of the 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. Each vein also gives off a dorsal branch that drains blood from the muscles of the...
on the right side of the body, and the hemiazygos vein and the accessory hemiazygos vein drain most of the posterior intercostal veins on the left side of the body. Specifically, the hemiazygos vein mirrors the bottom part of the azygos vein.
The structure of the hemiazygos vein is often variable. It usually begins in the left 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...
or renal vein
Renal vein
The renal veins are veins that drain the kidney. They connect the kidney to the inferior vena cava.It is usually singular to each kidney, except in the condition "multiple renal veins".It also divides into 2 divisions upon entering the kidney:...
, and passes upward through the left crus
Crus
Crus is the portion of the body starting from the ankle and ending at the knee. It is sometimes known as the gaiter...
of the diaphragm to enter the thorax
Thorax
The thorax is a division of an animal's body that lies between the head and the abdomen.-In tetrapods:...
. It continues ascending on the left side of the vertebral column
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...
, and around the level of the ninth thoracic vertebra, it passes rightward across the column, behind the aorta
Aorta
The aorta is the largest artery in the body, originating from the left ventricle of the heart and extending down to the abdomen, where it branches off into two smaller arteries...
, esophagus
Esophagus
The esophagus is an organ in vertebrates which consists of a muscular tube through which food passes from the pharynx to the stomach. During swallowing, food passes from the mouth through the pharynx into the esophagus and travels via peristalsis to the stomach...
, and thoracic duct
Thoracic duct
In human anatomy, the thoracic duct of the lymphatic system is the largest lymphatic vessel in the body. It is also known as the left lymphatic duct, alimentary duct, chyliferous duct, and Van Hoorne's canal....
, to end in the azygos vein
Azygos vein
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.-Structure:...
.
The hemiazygos may or may not be continuous superiorly with 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:...
.
It receives the 9th, 10th, and 11th 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. Each vein also gives off a dorsal branch that drains blood from the muscles of the...
and the 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....
of the left side, and some esophageal and mediastinal veins.
Etymology
The name for this vein is derived from that of the azygos veinAzygos vein
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.-Structure:...
. Azygos means 'unpaired', and hemi means half. This vein mirrors the bottom half the azygos vein.