<P> The atrium is the upper chamber in which blood enters the heart . There are two atria in the human heart , which receive blood - the left atrium from the lungs , and the right atrium from the venous circulation . The atria receive blood , and when the heart muscle contracts , pump blood to the ventricles . All animals with a closed circulatory system include at least one atrium / auricle ( humans have two atria ) . </P>
<P> The atrium is the upper chamber in which blood enters the heart . There are two atria in the human heart , which receive blood - the left atrium from the lungs , and the right atrium from the venous circulation . The atria receive blood , and when the heart muscle contracts , pump blood to the ventricles . All animals with a closed circulatory system include at least one atrium / auricle ( humans have two atria ) . </P>
where does right atrium pump blood when it contracts
where does right atrium pump blood when it contracts
venous circulation
venous circulation