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.
The major veins connected to the right atrium (a chamber of the heart) are the superior vena cava and the inferior vena cava. The superior vena cava returns blood from the upper body to the heart, and the inferior vena cava returns the blood from the lower part of the body. The superior vena cava is thin-walled, and the blood is under low pressure. It lies near lymph nodes in the chest.