Venous

Venous refers to the veins and the venous system, which carry blood toward the heart. In humans, veins operate under lower pressure than arteries and have thinner walls with greater capacity to hold blood. The venous system includes superficial veins near the skin and deeper veins within muscles, as well as specialized venous structures such as venous sinuses in the brain and the portal venous system in the liver. Major systemic veins include the superior and inferior vena cavae, which collect blood from the body, and the pulmonary veins, which return oxygenated blood from the lungs to the heart.

Veins function as capacitance vessels, able to expand and store blood. One key feature of many veins is the presence of valves that prevent backflow and help maintain unidirectional flow, especially in the limbs where blood must travel against gravity. Venous return depends on factors such as respiratory movements, muscle activity, and venous tone. The venous system plays a critical role in circulatory efficiency and blood volume distribution; disruptions can affect perfusion and pressure in the heart and lungs.

Common venous conditions include venous insufficiency, varicose veins, and venous ulcers, often resulting from valve failure or chronic venous hypertension. Deep vein thrombosis is a potentially serious condition where clots form in deep veins, typically in the legs, risking embolism. Diagnosis commonly uses duplex ultrasound; treatment ranges from compression therapy and lifestyle changes to anticoagulation, endovascular interventions, or surgery. Prevention focuses on mobility, weight management, and, in at-risk settings, prophylactic measures.