What is the double pump action of heart?
The double pump action of the heart refers to the coordinated contraction and relaxation of the heart's chambers, the atria (upper chambers) and ventricles (lower chambers), which ensures the efficient pumping of blood throughout the body. Here's an explanation of the double pump action:
1. Atrial Systole (Atrial Contraction):
- The heart's electrical signal, originating in the sinoatrial node (SA node), initiates atrial systole.
- The atria contract, increasing the pressure within them.
- This pressure forces the blood present in the atria into the ventricles through the open atrioventricular valves (tricuspid and mitral valves).
2. Ventricular Systole (Ventricular Contraction):
- Following atrial systole, ventricular systole occurs.
- The electrical signal reaches the ventricles, causing their contraction.
- As the ventricles contract, the pressure within them increases, exceeding the pressure in the atria and major arteries (aorta and pulmonary artery).
- The increased ventricular pressure causes the atrioventricular valves to close, preventing backflow of blood into the atria.
3. Semilunar Valve Opening and Blood Ejection:
- The pressure generated by ventricular contraction forces open the semilunar valves (aortic and pulmonary valves).
- The aortic valve opens, allowing oxygenated blood from the left ventricle to be pumped into the aorta, the main artery that supplies blood to the body's organs and tissues.
- Simultaneously, the pulmonary valve opens, allowing deoxygenated blood from the right ventricle to be pumped into the pulmonary artery, which carries blood to the lungs for oxygenation.
4. Ventricular Relaxation and Diastole:
- After ventricular systole, the ventricles relax and enter the diastole phase.
- As the ventricles relax, the pressure within them decreases, causing the semilunar valves to close.
- The closure of the semilunar valves prevents backflow of blood from the arteries into the ventricles.
- The atrioventricular valves remain closed during ventricular relaxation.
5. Atrial Diastole (Atrial Relaxation) and Filling:
- During ventricular diastole, the atria also relax and enter the diastole phase.
- The decreased pressure in the ventricles creates a pressure gradient that causes blood to flow from the vena cava (superior and inferior vena cava) and pulmonary veins into the right and left atria, respectively.
- The open atrioventricular valves allow the blood to flow into the ventricles.
6. Repeat of the Cycle:
- The relaxation phase (diastole) allows the heart chambers to fill with blood before the next contraction (systole) occurs.
- This coordinated sequence of atrial and ventricular systole and diastole repeats continuously, ensuring the continuous circulation of blood throughout the body.
The double pump action of the heart ensures that oxygenated blood is pumped to the body's tissues and organs, while deoxygenated blood is sent to the lungs for oxygen replenishment. This synchronized mechanism is crucial for maintaining adequate blood flow and meeting the oxygen and nutrient demands of the body's cells.