A blood cell in a vein draining the brain enters the superior vena cava. The first heart chamber it enters is the [1], which contracts to send it through the [2] valve. Now it is in the [3], which contracts to propel the blood cell past the [4] valve through the [5]. It goes through smaller and smaller blood vessels until it reaches the [6]. Freshly oxygenated, the blood cell travels through [7] to reach the first heart chamber, the [8], which contracts to send it past the [9] valve. Now it is in the [10], which contracts to eject the blood past the [11] valve and up through the [12], to the rest of the body.