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.
Carbon dioxide moves from the cells and into the capillaries. Blood leaves the capillary and enters the small venules. 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.