Job: Works with the respiratory system to complete respiration.
Composite: Heart, blood vessels and blood.

Cardiovascular System
The cardiovascular system works with the respiratory system to complete respiration. Respiration is the exchange of the gases between the air we breathe, the blood in the body, and the cells the body.
The cardiovascular system is made up of the heart, blood vessels, and blood. In addition to getting oxygen and nutrients to the cells of the body, the cardiovascular system also removes wastes, keeps the temperature of the body even, and uses clotting to prevent loss of blood when the body is injured.
The arteries are larger when they are closer to the heart, they get smaller as they move away from the heart, branching into arterioles. arterioles deliver the blood into capillaries, which are microscopic blood vessels. These branch and form a network throughout the distal tissues. These capillary beds are the location where the respiration, or exchange of nutrients and wastes, occurs. Capillary blood now begins it's trip back to the heart. First, it moves through the small vessels called venues. As the blood gets closer to the heart, the vessels carrying it combine to form veins.
The heart is really a muscle. It's located to the left of the middle of the chest, and it's about the size of a fist. The heart is responsible for sending blood out into the body. The blood provides the body with oxygen and nutrients. Then the waste produced during this exchange travels back to the lungs for elimination.
The heart is made up of four different areas, and each of these is called a chamber. There are two chambers on each side of the heart. One chamber is on top and one is on the bottom on each side. The two chambers on top are called the atria and the two chambers on the bottom are called the ventricles. Running down the center of the heart is a thick wall of muscle called the septum which separates the left and right sides of the heart.
The atria and ventricles work as a team, the atria fill with blood, then dump it into the ventricles. While the ventricles pump the blood out of the heart, the atria refill and get ready for the next contraction.
There are four valves in the heart, the mitral valve and the tricuspid valve work between the atria and ventricles. The other two are called the aortic valve and the pulmonary valve, and they control the flow of the blood as it leave the heart. These valves work to keep the flow of blood moving forward. They open up to let the blood move ahead, and then close quickly to prevent the blood from moving backward.





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