Explain why the heart is considered a double pump. Trace the path of blood from the right atrium back to the right atrium, naming the chambers of the heart and their vessels through which the blood passes. (p. 281)

The heart is considered a double pump because it pumps blood through two separate circuits: the pulmonary circuit (to the lungs) and the systemic circuit (to the rest of the body). The right side of the heart pumps blood through the pulmonary circuit, while the left side pumps blood through the systemic circuit. In this exercise, we will focus on the path of blood from the right atrium back to the right atrium, starting with the pulmonary circuit.

The pulmonary circuit begins with the flow of blood from the right atrium. When the right atrium contracts, blood passes through the tricuspid valve into the right ventricle. Upon contraction of the right ventricle, blood is pumped through the pulmonary valve into the pulmonary artery, which carries oxygen-poor blood to the lungs.

In the lungs, oxygen-poor blood releases carbon dioxide and picks up oxygen, becoming oxygen-rich blood. This oxygen-rich blood then returns to the heart via the pulmonary veins.

Oxygen-rich blood from the pulmonary veins enters the left atrium. The left atrium contracts, pushing blood through the bicuspid (mitral) valve into the left ventricle. Upon contraction of the left ventricle, blood is pumped through the aortic valve into the aorta, which is the main artery that carries oxygen-rich blood to the rest of the body.

The systemic circuit ends with oxygen-poor blood being returned to the heart through two large veins called the superior and inferior vena cava. Oxygen-poor blood from the upper body flows through the superior vena cava, while blood from the lower body flows through the inferior vena cava. Both of these veins empty into the right atrium, completing the circulation loop. To summarize the path of blood through the heart: 1. Right atrium (through tricuspid valve) 2. Right ventricle (through pulmonary valve) 3. Pulmonary artery (to the lungs) 4. Pulmonary veins (from the lungs) 5. Left atrium (through bicuspid/ mitral valve) 6. Left ventricle (through aortic valve) 7. Aorta (to the rest of the body) 8. Superior and inferior vena cava (returning oxygen-poor blood to the right atrium)