Final answer:
Edema occurs when venous flow is restricted, causing increased pressure and fluid leakage into surrounding tissues. This condition can be aggravated by varicose veins and PAD. The cardiovascular system's blood flow is usually regulated by a branching network of arteries, arterioles, and capillaries, but this can be disrupted by such ailments.
Step-by-step explanation:
When arterial blood flow continues into an extremity but venous flow is impeded from returning to the system, the resulting physiological condition is known as edema. This accumulation of fluid occurs because the pressure in the capillaries increases as a result of the backup in venous blood, which then forces fluid to exit the capillaries and enter the surrounding tissue.
The cardiovascular system maintains the flow of blood through a series of branching vessels, with arteries that subdivide into smaller arterioles and lead to capillaries. The equation of continuity ensures that the sum of the flow rates in these branching vessels is consistent. However, when venous return is restricted, this continuity is disrupted and can lead to the aforementioned edema, potentially aggravating other conditions such as varicose veins and Peripheral Artery Disease (PAD), where symptoms like intermittent claudication can occur.
Additionally, the superficial veins in the limbs can play a role in temperature regulation by diverting more blood to the surface to dissipate heat in warm temperatures, or by constricting to conserve heat in cold weather.