Atrium (heart)

The atrium (plural: atria) is one of the two blood collection chambers of the heart. It was previously called the auricle, but that name is now used for an appendage of the atrium. The atrium is a chamber in which blood enters the heart, as opposed to the ventricle, where it is pushed out of the organ. It has a thin-walled structure that allows blood to return to the heart. There is at least one atrium in animals with a closed circulatory system.

Atrium (heart)

The atrium (plural: atria) is one of the two blood collection chambers of the heart. It was previously called the auricle, but that name is now used for an appendage of the atrium. The atrium is a chamber in which blood enters the heart, as opposed to the ventricle, where it is pushed out of the organ. It has a thin-walled structure that allows blood to return to the heart. There is at least one atrium in animals with a closed circulatory system.