The venule is defined as the small blood vessel that collects the blood from the capillaries and drains the blood into the larger veins. Blood capillaries are the finest blood vessels that reach each and every cell of the body. The capillaries gradually reunite and increase in size. The smallest united common branch of the capillaries is called a venule. The venules join to form larger veins.

Lymph is a transparent fluid of the lymphatic system that is derived from the blood and other tissues and accumulates in the interstitial spaces, therefore called the interstitial fluid. Lymph contains the leucocytes mainly the lymphocytes. This fluid has a composition similar to plasma except that it is low in protein.