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No valve divides the superior vena cava from the right atrium. The superior vena cava is made up of three layers, starting with the innermost endothelial tunica intima . The middle layer is the tunica media , composed of smooth muscle tissue, and the outermost and thickest layer is the tunica adventitia , composed of collagen and elastic ...
In anatomy, the venae cavae (/ ˈ v iː n i ˈ k eɪ v i /; [1] sg.: vena cava / ˈ v iː n ə ˈ k eɪ v ə /; from Latin 'hollow veins') [2] are two large veins (great vessels) that return deoxygenated blood from the body into the heart. In humans they are the superior vena cava and the inferior vena cava, and both empty into the right atrium ...
In prenatal development, the eustachian valve helps direct the flow of oxygen-rich blood through the right atrium into the left atrium and away from the right ventricle. Before birth, the fetal circulation directs oxygen-rich blood returning from the placenta to mix with blood from the hepatic veins in the inferior vena cava. Streaming this ...
There are no valves in the veins of the thorax or abdomen. [4] There is a valve at the junction of the inferior vena cava (one of the great vessels) and the right atrium known as the valve of inferior vena cava also known as the eustachian valve. This valve is an embryological remnant and is insignificant in the adult.
The inferior vena cava is a large vein that carries the deoxygenated blood from the lower and middle body into the right atrium of the heart. 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 azygos vein transports deoxygenated blood from the posterior walls of the thorax and abdomen into the superior vena cava.. It is formed by the union of the ascending lumbar veins with the right subcostal veins at the level of the 12th thoracic vertebra, ascending to the right of the descending aorta and thoracic duct, passing behind the right crus of diaphragm, anterior to the vertebral ...
Oxygen-deprived blood from the superior and inferior vena cava enters the right atrium of the heart and flows through the tricuspid valve (right atrioventricular valve) into the right ventricle, from which it is then pumped through the pulmonary semilunar valve into the pulmonary artery to the lungs.
Vena cava compression: An increase in the resistance of the vena cava, as occurs when the thoracic vena cava becomes compressed during a Valsalva maneuver or during late pregnancy, decreases return. Gravity : The effects of gravity on venous return seem paradoxical because when a person stands up, hydrostatic forces cause the right atrial ...