venül

Venules are very small veins in the body. They are the smallest veins and are responsible for collecting deoxygenated blood from capillaries. Capillaries are the tiniest blood vessels where the exchange of oxygen, nutrients, and waste products occurs between the blood and the body's tissues. After blood passes through the capillary beds, it enters the venules.

Venules are typically between 10 and 100 micrometers in diameter. Their walls are thin, consisting of an inner layer of endothelium, a middle layer of smooth muscle, and an outer layer of connective tissue. The thin walls of venules, particularly the postcapillary venules, allow for some passage of white blood cells and fluid from the bloodstream into the surrounding tissues, a process important in inflammation and immune responses.

As venules merge and increase in size, they form larger veins. These larger veins then transport the deoxygenated blood back towards the heart. The collective function of venules is crucial for the circulatory system's ability to return blood to the lungs for reoxygenation. They act as a vital bridge between the microcirculation (capillaries) and the larger venous network.