STRUCTURES AND

FUNCTIONS OF THE CIRCULAT

ORY SYSTEM

HeartThe heart is the main organ in the circulatory system and without it we would die its main purpose is to circulate blood around the body. The heart works like this:

1. de-oxygenated blood gets in the right atrium into the Vena Cava.2. The blood passes through a valve in the right ventricle. 3. From there travels up to the lungs into the pulmonary artery.4. The blood gets oxygenated in the lungs and comes back down to the left atrium, through the pulmonary vein.5. From the left atrium it goes through another valve in the left ventricle.6. Last the blood is pumped throughout the body through the aorta.

red blood cellsRed blood cells are one of the key things in the circulatory system. They get produced in the bonemarrow and are transported for 120 days until they are destroyed in the spleen. When these get destroyed the iron inside of them is preserved and stored in the liver.

Spleen- acts as a filter for blood in the immune system, recycles red blood cells, stores platelets and white blood cells. The spleen also fights bacterias.

Liver- his main job is to filter the blood that comes from the digestive tract and detoxifies chemicals and metabolizes drugs before pumping it to the body.

white blood cellsWhite blood cells are also one of the keys in the circulatory system. Like the red blood cells are produced in the bone marrow. The function of these ones is to fight with micro-organisms and they also help strengthen the immune system. They are involved in protecting the body against infectious disease and foreign invaders. All blood cells have nuclei that distinguish them from the red blood cells and the platelets.

arteriesArteries are elastic tubes that carry blood away from the heart. When arteries move away from the heart they divide in small vessels. The biggest arteries are as big as a thumb and the smallest arteries are thinner than a hair these thinner arteries are called arterioles. Arteries carry bright red blood and the color comes from the oxygen it carries.

veinsVeins carry the blood to the heart. The smallest veins are called venules and are very thin. They join larger veins that open in the heart. The veins carry dark red blood that doesn't have much oxygen. Veins have thin walls. They are not as strong as the arteries because as blood is returned to the heart, it is under less pressure.