The cardiovascular system

the heart description and heart cycles. 

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The Heart- delivering food and oxygen to all body

The heart is a double pump, two hearts beat as one. The right side pumps blood to the lungs for oxygenation, then it returns to the left side of the heart which pumps the oxygenated blood around the rest of the body. 

If the heart was all a single pump and single circulation, then teh heart would have to be very big in size and would require alot more energy to pump the blood around the body once. 

It is made of cardiac muscle. 

The heart has it's own blood supply, the coronary arteries around the heart bring oxygenanated blood from the aorta, also cardiac veins to bring the deoxygenated blood back. (,r:11,s:15,i:196&tx=40&ty=22)

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Sections of the heart.

The heart has four chambers, left and right atrium, the left ventricle and the right ventricle. 

They are separated by atrioventricular valves.

The right side- the tricuspid valve

The left side- bicuspid valve. 

These valves ensure the blood flows in one direction only. 

Two main arteries (away from the heart) AORTA to the body pulmonary artery to the lungs. These have semi-lunar pocket valves at their entrances. 

Two main veins-vena cava from the body, pulmonary vein from lungs. 

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The Cardiac Cycle

The cycle is cordinated by the "pacemaker" the sinoatrial node(SAN) in the right atrium. Both sides of the heart work together. 

Atrial Systole

both atria contract

*blood flows into ventricles backflow is prevented by valves in veins closing. semi lunar valves in the arteries are closed. 

Ventricular Systole

*both ventricles contract

*atrioventricular valves (bicusppid and tricuspid) close, preventing backflow into atria. blood flows into arteries. 


*atria and ventricles all relax

blood continues to flow into the atria. 

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Coordination of Cardiac cycle

Sino atrial node initiates cycle.

* a wave of depolarisation spreads over atria.

atrail muscle contracts all over

wave of depolarisation reaches atrio ventricular node(AV NODE)

message continues down fibres in the septum(bundle of his )

then up the ventricle walls.

Ventricles contract 

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blood vessels


Arteries carry only oxygenated blood. (except pulmoonary circulation)

They are not permeable to oxygen and carbon dioxide at the same time. They always carry blood to the organs. They do not have valves (except in the heart)


Cappilaries carry bothe oxygenated and de-oxygenated blood. They do not have valves (except in the heart)


veins only carry de-oxygenated blood. They always carry blood away from organs towards the heart. They have valves to prevent backflow of the blood at such a low pressure. 

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