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 two principal vessels are the great cardiac vein, which drains blood from the anterior surface of the heart, and the middle cardiac vein, which drains the heartâs posterior surface. These vessels transport blood into an opening called the coronary sinus, which returns blood to the right atrium (see Fig. 22-4).