The Heart

The heart organ is a &double pumpOxygenated blood &from the lungs enters the &left &side of the heart and is pumped &to the rest of the body (the systemic circuit)The left ventricle has a thicker muscle wall than the right ventricle &as it has to pump blood at high pressure around the &entire body,

Deoxygenated blood &from the body enters the &right &side of the heart and is pumped &to the lungs (the pulmonary circuit)The right ventricle is pumping blood at lower pressure to the &lungs

A muscle wall called the &septum &separates the two sides of the heart

Blood is pumped &towards &the heart in &veins &and &away &from the heart in &arteriesThe &coronary &arteries &supply the &cardiac muscle tissue &of the heart with oxygenated bloodAs the heart is a muscle it needs a constant supply of oxygen (and glucose) for aerobic respiration to release energy to allow continued muscle contraction

Valves &are present to &prevent blood flowing backwards & The pathway of blood through the heartDeoxygenated blood &coming from the body flows through the &vena cava &and into the &right atriumThe &atrium &contracts &and the blood is forced through the &tricuspid (atrioventricular) valve &into the &right ventricleThe ventricle &contracts &and the blood is pushed through the &semilunar valve &into the &pulmonary arteryThe blood travels to the &lungs &and moves through the capillaries past the alveoli where &gas exchange &takes placeLow pressure &blood flow on this side of the heart prevents damage to the capillaries in the lungs

Oxygenated blood &returns &via the &pulmonary vein &to the &left atriumThe &atrium contracts &and forces the blood through the &bicuspid (atrioventricular) valve &into the &left ventricleThe ventricle &contracts &and the blood is forced through the &semilunar valve &and out through the &aortaThicker muscle walls of the left ventricle produce a &high enough pressure &for the blood to travel around the whole body