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.
Right pulmonary veins. Veins are the blood vessels that carry blood to the heart. Pulmonary veins are responsible for carrying oxygenated blood from the lungs back to the left atrium of the heart. This differentiates the pulmonary veins from other veins in the body, which are used to carry deoxygenated blood from the rest of the body back to the heart.