Heart valves and their functions

v About this view: 
The heart's interior comprises two upper  chambers, the atria, and two lower  chambers, the ventricles. Atrioventricular  (AV) valves between the atria and  ventricles, and semilunar valves between  the ventricles and the arteries outside the  heart, regulate the direction of blood flow, 
The right atrium receives deoxygenated  blood from the systemic circulation via the  vena cavae. The right ventricle receives that  blood from the atrium, then contracts to  eject it through the pulmonary arteries to  the lungs. Simultaneously, the left atrium  receives oxygenated blood from the lungs  via the pulmonary veins. The left ventricle  receives that blood from the atrium, then  contracts to eject it through the aorta to  the systemic circulation 
The AV valves open to allow blood flow  from the atria to the ventricles. When the  ventricles contract, the AV valves close to  prevent backflow. Simultaneously,  ventricular contraction forces the semilunar  valves open, allowing for blood ejection.  When contraction finishes, the semilunar  valves shut to prevent backflow from the  arteries. 
Right ventricle  Ventriculus dexter 
v About this view:  The right atrium receives deoxygenated  blood from the systemic circulation via the  superior and inferior vena cavae. The right  ventricle receives that blood from the  atrium, then contracts to eject it through  the pulmonary arteries to the lungs for gas  exchange 
Lett ventricle Ventriculus sinister
v About this view: The left atrium receives oxygenated blood from the lungs via the pulmonary veins. The left ventricle receives that blood from the atrium, then contracts to eject it through the aorta to the systemic circulation.,

V Atrioventricular valves  Valvae atrioventriculares 
v About this view:  The two atrioventricular (AV) valves are the  tricuspid valve, between the right atrium  and right ventricle, and the mitral valve,  between the left atrium and left ventricle  The cusps of both valves are membranous  folds, connected by fibrous tendons (the  chordae tendineae) to papillary muscles  that project from the ventricle walls. 
When the atria are full and the ventricles  relax, the AV valves are pushed open to  allow blood flow. When the ventricles  contract, the increased ventricular pressure  pushes the AV valves closed, and the  papillary muscles pull down on the chordae  tendineae. This stops the valve cusps from  blowing back into the atria during  contraction, and so prevents backflow  (regurgitation) of blood. 
V
Pulmonary valve Valva trunci pulmonalis
v About this view: The two semilunar valves are the pulmonary valve, between the right ventricle and the pulmonary trunk, and the aortic valve, between the left ventricle and the aorta.
Ventricular contraction forces the semilunar valves open, allowing for blood ejection. When contraction finishes, increased pressure in the arteries pushes the semilunar valves shut, preventing backflow (regurgitation) of blood.
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