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The circulatory system is the system by which blood travels throughout the body. In this system the exchange of gases and nutrients takes place.

This system contains of three mian organs

1. Heart

2. Lungs

3. Blood vessels

The heart

1. The heart has four chambers: left atrium, left ventricle, right atrium, right ventricle

2. The left side of the heart pumps oxygenated blood where as the right side of the heart pumps Deoxygenated blood.

3. Which side of the heart has a vein and an artery.

4. On the left side of the heart there is the aorta and the pulmonary vein

5. On the right side of the heart there is Vena Cava and the pulmonary artery

6. The heart also has valves which prevent the blood to go backwards.(on each side)

Blood vessels

1. There are three types of blood vessels: arteries, veins, capillaries

2. arteries carry the blood away from the heart whereas veins carry the blood towards the heart.

3. Caterpillars are one cell thick and they connect the arteries to the veins. This is where the exchange of gases happens

4. Veins also have valves which prevents the blood to go backwards

Timeline

1. The deoxygenated blood from the body returns to the heart to get pumped to the lungs.

2. The Pulmonary artery takes the deoxygenated blood to the lungs

3. In the lungs the blood gets oxygenated and then returns to the heart to get pumped through the body.

4. It gets returned by the pulmonary vein.

5. The heart the blood gets pumped through out the body.

6. The aorta takes the blood from the heart.

7. In the body the oxygen gets diffused and returns to the heart from the vena cava.

8. And the whole cycle is repeated.

# data[].attributes.body
The circulatory system is the system which transports substances around the body in the blood. These substances are oxygen, carbon dioxide, amino acids, fatty acids, glycerol and glucose. The pumping action of the heart transports the blood to the body through blood vessels.

Timeline (The path of blood is) :
1. First the deoxygenated blood in our body moves from the capillaries to the vena cava which is a vein which leads the blood to the right atrium.
2. From the right atrium the blood moves to the right ventricle through the tricuspid valve and from there it enters the pulmonary artery through pulmonary valve. The pulmonary artery takes the blood to the lungs.
3. In lungs the artery splits into capillaries so that it is easier for substances like oxygen and glucose to pass between the blood and tissues in a short amount of time. Then the capillaries get bigger forming the pulmonary vein and the oxygenated blood is carried to the left atrium.
4. From the left atrium the blood moves to the left ventricle through the mitral valve and from there enters the aorta (artery) through aortic valve. The aorta carries blood away from the heart to the body and then the process keeps on repeating.

# data[].attributes.body
The circulatory system is an important organ system of our body which consists of the heart, veins, arteries, capillaries and blood. it has 3 main functions:
1. It helps in transporting oxygen to all cells in our body
2. It helps in taking waste materials like carbon dioxide and urea to the excretory organs.
3. It protects the body from diseases like viruses, germs and bacteria.

timeline of blood (throughout the body)

1. Oxygenated blood is pumped out of the left ventricle into the aorta which is the largest artery in our body.
2. The aorta splits into arterioles and then into capillaries when it is close to an organ.
3. The capillaries then diffuse the oxygen to all the cells and take the carbon dioxide from them.
4. This deoxygenated blood in the capillaries now join again to form venules and then veins.  The blood is sent to the right atrium through the vena cava, which is the largest vein in our body.
5. The deoxygenated blood goes into the right ventricle by the tricuspid valve. it is then sent to the lungs via the pulmonary artery. It is the only artery which contains deoxygenated blood.
6. The blood is oxygenated in the lungs and sent back to the left side of the heart via the pulmonary vein into the left atrium. It is the only vein which contains oxygenated blood.
7. From the left atrium, the blood is sent back to the left ventricle by the  mitral valve.
8. This whole cycle is repeated again and again all day long

# data[].attributes.body
The deoxygenated blood comes back from the body, deprived of oxygen, through the Vena Cava to the right atrium in the heart.

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The pulmonary artery branches into small capillaries in the lungs. Air sacs known as alveoli fill up with oxygen when we inhale. The haemoglobin in the red blood cells (in the blood) absorb the oxygen and refill the sacs with CO₂.

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The capillaries slowly merge and form the pulmonary vein. This vein transports the oxygenated blood to the left artrium.

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The atrium, after being filled up, pushes the blood to the left ventricle, through the Mitral valve, where they pump the blood to the aorta through the aortic valve.

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The aorta takes the blood to the body where it again splits up into smaller arteries, and into capillaries. The nutrients and oxygen will diffuse through the walls of the capillaries and will be supplied to the cells while CO₂ diffuses out of the cell membrane and into the capillaries.

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The small capillaries start to merge and form bigger and bigger veins. They end up in the Vena Cava and into the left atrium and the cycle repeats.

# data[].attributes.body
The circulatory system is a system in which substances such as oxygen , nutrients etc. are transported to our body . The blood carries substances such as oxygen , carbon dioxide, glucose , amino acids , glycerol and fatty acids. Our heart then pumps this blood to all the tissues and organs of our body.

Timeline ( blood path )
1. The deoxygenated blood from our body enters the right side of the heart with the help of capillaries and it enters through the vena cava ( it is a vein ) .
2. Then the deoxygenated blood enters the right atrium and then goes through the tricuspid valve and enters the right ventricle . From there it goes into the pulmonary valve and then into the pulmonary artery . The pulmonary artery will then take this blood to the lungs.
3. In the lungs the capillaries will take in oxygen and the blood will get oxygenated .
4. This oxygenated blood will then return to the left side of the heart with the help of the pulmonary vein. Once it has entered the heart, the blood will enter the left atrium and will go through the Mitrle valve and enter the left ventricle. After that it will go through the Aortic valve and enter the Aorta .
5. Then the heart will pump the blood through the Aorta and the blood will go to all the organs of the body. In the organs the capillaries will spread out and diffuse the oxygen to the organs .
6. Then this blood will go back to the heart and this cycle will continue to repeat !