ERA. 1  baseball, baseball game - a ball game played with a bat and ball between two teams of nine players; teams take turns at bat trying to score runs; he played baseball in high school; there was a baseball game on every empty lot; there was a desire for National League ball in the area; play ball!.
The contraction of the heart muscle starts in the two atria, which push the blood into the ventricles. Then the walls of the ventricles squeeze together and force the blood out into the arteries: the aorta to the body and the pulmonary artery to the lungs.
The aorta is the largest artery and is connected directly to the heart. When blood flows from the heart and is forced into the arteries, they must expand to accept the blood and then contract to squeeze the blood into the veins as the heart relaxes between beats. This means that arteries need to be elastic to keep expanding and contracting. When the heart relaxes, it is the job of the arteries to maintain blood pressure and keep it moving forward. Arteries maintain the minimum needs of blood pressure. If they did not work, blood pressure would be closer to 120/0 instead of 120/80.