Superior Vena Cava.
The superior vena cava (SVC), also called the precava, is a short vein having a large diameter formed by the left and right brachiocephalic veins which are also called the innominate veins. It is also joined by the azygos vein, which drains the rib cage, just before entry of the SVC into the right atrium of the heart.
Function of the Superior Vena Cava.
The superior vena cava drains the deoxygenated blood from the upper part of the body into the right atrium of the heart. The upper part of the body includes the head, neck and both upper extremities.
The opening between the superior vena cava and the right atrium is not guarded by any valve. The pulsations caused by the contraction of the right atrium and right ventricle is therefore seen in the jugular veins in the neck.
Dimensions of Superior Vena Cava.
The size of the superior vena cava is given below:
Length = 7 cms.
Diameter = 2 cms.
Course of Superior Vena Cava.
Te superior vena cava is siyuated in the middle of the chest. It begins just below the coastal cartilage of the first rib near the sternum (breast bone). It descends vertically behind the first and second intercoastal spaces to end in the right atrium just opposite the upper border of the third coastal cartilage on the right side of the sternum. Its course describes a slight convexity towards the right. The lower half of the superior vena cava is enclosed within the pericardial sac of the heart and the upper half is outside.
Picture showing superior vena cava.
Structures Relating to Superior Vena Cava.
In front between the SVC and the first and second intercoastal spaces are the anterior borders of the right lung and pleura. In its lower half, however the pericardium intervenes.
Behind it are the root of the right lung and the right vagus nerve.
On its Right Side are the right pleura and the right phrenic nerve.
On its Left Side lie the brachiocephalic artery and the ascending aorta.
The lower half of the SVC is covered with the pericardium and it receives the azygos vein just before being covered by the heart sac.
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