<Tr> <Th> FMA </Th> <Td> 7099 </Td> </Tr> <Tr> <Td_colspan="2"> Anatomical terminology (edit on Wikidata) </Td> </Tr> <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 used to be called the "auricle", and that term is still used to describe this chamber in, for example, the Mollusca, but in humans that name is now used for an appendage of the atrium . </P>

Where does the blood in the right atrium come from