Systolic and diastolic pressure in systemic circulation is 120 and 70 mmHgwhere as in the pulmonary circulation these are 24 and 8 mmHgrespectively• What causes this pressure difference?

The pressure difference between the systemic and pulmonary circulation is primarily due to the difference in the resistance and the work load between the two circulatory systems.

1. Resistance: The systemic circulation (which transports blood to most of the body) has much more resistance compared to the pulmonary circulation (which only transports blood to the lungs). This is because the systemic circulation has longer vessels and more arterioles and capillaries, which increase resistance. The higher resistance in the systemic circulation means that the heart has to generate more pressure to overcome it.

2. Workload: The left ventricle, which pumps blood into the systemic circulation, has to generate enough force to push the blood throughout the entire body. On the other hand, the right ventricle, which pumps blood into the pulmonary circulation, only has to push the blood to the lungs. Therefore, the workload on the left ventricle is much higher, which results in higher pressure.

3. Blood Volume: The systemic circulation also handles a much larger volume of blood compared to the pulmonary circulation, which also contributes to the higher pressure.

In summary, the pressure difference is caused by the difference in resistance, workload, and blood volume between the systemic and pulmonary circulations.