Vein
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A vein is a blood vessel in the circulatory system of humans and most other animals that carries blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; except
Layers of vein wall shown in comparison to arterial wall
Main veins of the systemic circulation
Deep and superficial veins of the arm and near thorax
Diagram of different sized veins with differing component proportions
Atrium (heart)
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The atrium is one of the two upper chambers in the heart that receives blood from the circulatory system. The blood in the atria is pumped into the heart ventricles through the atrioventricular mitral
Right heart anatomy, right ventricle seen on right of illustration
Left atrial appendage shown at upper right
CT scan of the chest showing a thrombus in the left atrial appendage (left: axial plane, right: coronal plane)