Where does the fluid that leaks out of the capillaries go?

Final answer:

The fluid that leaves the capillaries enters the interstitial space and is absorbed by the lymphatic vessels, forming lymph. This lymph passes through the lymph nodes for filtration and finally returns to the blood circulation through the subclavian veins.

Explanation:

The fluid that leaks out of the capillaries goes into the surrounding tissue spaces as interstitial fluid, a portion of which is then absorbed by the lymphatic vessels, forming lymph. This excess fluid is eventually returned to the blood circulation.

The lymphatic system plays a crucial role in this process by picking up the fluid that is not reabsorbed into the blood capillaries and directing it through a network of vessels and nodes that filter and clean it before returning it to the bloodstream via the subclavian veins.

Proteins and other large solutes are generally too large to pass through the capillary walls, leading to the formation of a hyperosmotic solution inside the capillaries. About 85% of the watery plasma that leaves the capillaries diffuses back into them near the venules, while the remaining 15% is collected by the lymphatic vessels.

Lymph, which is now similar in composition to plasma, passes through lymph nodes where it is filtered by white blood cells that remove infectious agents before it returns to the heart.