Inductive definition of CW complexes. If the largest dimension of any of the cells is n, then the CW complex is said to have dimension n. If there is no bound to the cell dimensions then it is said to be infinite-dimensional. The n-skeleton of a CW complex is the union of the cells whose dimension is at most n.
Deoxygenated blood enters the right atrium through three major veins: the superior and inferior vena cava and the coronary sinus. The superior vena cava returns all of the blood to the heart from tissues superior to the heart in the head, neck, arms and upper thorax.
These venules become progressively larger vessels called veins. The vena cava are the two largest veins that carry blood into the right upper chamber of the heart (the right atrium). The superior vena cava carries blood from the brain and arms into the top of the right atrium. The inferior vena cava carries blood from the legs and abdominal cavity into the bottom of the right atrium. The vena cava are also called the central veins. Central venous catheters are inserted with the tip in or close to the superior of inferior vena cava. Blood is pumped from the right side of the heart into the blood vessels of the lung.