Explain how the contraction and relaxation of chamber walls move blood through he heart?
The contraction and relaxation of the heart's chamber walls are essential for pumping blood throughout the body. The heart consists of four chambers: two atria (upper chambers) and two ventricles (lower chambers). The contraction and relaxation of these chambers in a coordinated manner enable blood to flow in and out of the heart, ensuring continuous circulation. Here's an overview of how the contraction and relaxation of the heart's chamber walls move blood:
1. Atrial Contraction (Systole):
- During atrial systole (contraction), the right and left atria contract simultaneously.
- This contraction increases the pressure within the atria and forces blood into the corresponding ventricles below them.
- The atrioventricular valves (tricuspid valve on the right side and mitral/bicuspid valve on the left side) are open during this phase, allowing blood to flow freely into the ventricles.
2. Ventricular Contraction (Systole):
- After the atria contract, the ventricles contract almost immediately, also known as ventricular systole.
- The contraction of the ventricles creates high pressure within them, causing the atrioventricular valves to close. This prevents backward flow of blood into the atria.
- The increased pressure forces the blood in the ventricles to push against the semilunar valves (pulmonic valve on the right side and aortic valve on the left side).
3. Opening of Semilunar Valves:
- The pressure exerted by the ventricular contraction exceeds the pressure within the major arteries (pulmonary artery on the right side and aorta on the left side), causing the semilunar valves to open.
- As the semilunar valves open, blood is ejected out of the ventricles into the pulmonary artery (carrying deoxygenated blood to the lungs) and the aorta (transporting oxygenated blood to the rest of the body).
4. Ventricular Relaxation (Diastole):
- After contraction, the ventricles relax, initiating ventricular diastole.
- The decrease in pressure within the ventricles allows the semilunar valves to close, preventing backflow of blood into the ventricles.
- Simultaneously, the atrioventricular valves open again, allowing blood from the atria to fill the relaxed ventricles.
5. Atrial Filling:
- During ventricular diastole, blood passively flows from the atria into the ventricles due to the pressure gradient created by the relaxation of the ventricles.
- This process continues until the ventricles are filled, and the cycle repeats itself with the next atrial contraction.
The coordinated contraction and relaxation of the atria and ventricles, along with the opening and closing of heart valves, ensures a continuous flow of blood through the heart. The right side of the heart pumps deoxygenated blood to the lungs for oxygenation, while the left side of the heart pumps oxygenated blood to the body's tissues and organs, sustaining the vital functions of the body.