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「 The inferior vena cava ( or IVC ) is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. Its walls are rigid and it has valves so the blood does not flow down via gravity. It is formed by the joining of the right and the left common iliac veins, usually at the level of the fifth lumbar vertebra.
The inferior vena cava is the lower ("inferior") of the two venae cavae, the two large veins that carry deoxygenated blood from the body to the right atrium of the heart: the inferior vena cava carries blood from the lower half of the body whilst the superior vena cava carries blood from the upper half of the body. Together, the venae cavae (in addition to the coronary sinus, which carries blood from the muscle of the heart itself) form the venous counterparts of the aorta.
It is a large retroperitoneal vein that lies posterior to the abdominal cavity and runs along the right side of the vertebral column. It enters the right auricle at the lower right, back side of the heart. The name derives from Latin : vena, "vein", cavus, "hollow".
【 語 句 】
・ deoxygenated ： 脱酸素化した ・ right atrium ： 右心房 ・ rigid ： 硬くて曲がらない？ ・ common iliac veins ： 総腸骨静脈 ・ lumbar vertebra ： 腰椎 ・ whilst～ ： ～する一方で ・ coronary sinus ： 冠静脈洞 ・ counterpart ： よく似たもの ・ aorta ： 大動脈 ・ retroperitoneal ： 後腹膜の ・ abdominal cavity ： 腹腔 ・ vertebral column ：脊 柱 ・ auricle ： 外耳
【 Structure 】
The inferior vena cava is formed by the joining of the left and right common iliac veins and brings collected blood into the right atrium of the heart. It also joins with the azygos vein (which runs on the right side of the vertebral column) and venous plexuses next to the spinal cord. Despite the previous paragraph, the inferior vena cava does not have any valves.
The inferior vena cava begins as the left and right common iliac veins behind the abdomen unite, at about the level of L5. It passes through the thoracic diaphragm at the caval opening at the level of T8.
【 Tributaries 】
The specific levels of the tributaries are as follows:
・ T 8 ： hepatic veins （ 肝静脈 ）, inferior phrenic vein （ 下横隔静脈 ）
・ L 1 ： right suprarenal vein （ 右副腎静脈 ）, renal veins （ 腎静脈 ）
・ L 2 ： right gonadal vein （ 生殖腺静脈 ）
・ L 1 ～ L 5 ： lumbar veins （ 腰静脈 ）
・ L 5 ： common iliac veins （ 総腸骨静脈 ）
Because the inferior vena cava is located to the right of the midline, drainage of the tributaries is not always symmetrical. On the right, the gonadal veins and suprarenal veins drain into the inferior vena cava directly. On the left, they drain into the renal vein which in turn drains into the inferior vena cava. By contrast, all the lumbar veins and hepatic veins usually drain directly into the inferior vena cava.
【 語 句 】
・ azygos vein ： 奇静脈 ・ spinal cord ： 脊髄 ・ diaphragm ： 横隔膜 ・ caval opening ： 大静脈孔
【 Development 】
In the embryo, the inferior vena cava and right auricle are separated by the valve of the inferior vena cava, also known as the Eustachian valve. In the adult, this valve typically has totally regressed or remains as a small fold of endocardium.[1]
【 Variation 】
Rarely, the inferior vena cava may vary in its size and position. In transposition of the great arteries the inferior vena cava may lie on the left. It may be replaced by two vessels beneath the level of the renal veins.[2]
【 Function 】
The inferior vena cava is a vein. It carries deoxygenated blood from the lower half of the body to the right atrium of the heart.[2]
The corresponding vein that carries deoxygenated blood from the upper half of the body is the superior vena cava. 」
【 語 句 】
・ embryo ： 胎児 ・ Eustachian valve ： 下大静脈弁 ・ regressed ： 退行して ・ endocardium ： 心内膜 ・ transposition ： 転移
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