Learning Objective
By the end of this lesson, the learner should be able to describe how lymphatics maintain low interstitial fluid volume and protein content, explain how lymphatic flow changes with interstitial pressure, and outline the pathway by which lymphatics return fluid and proteins to the systemic circulation.
Lymphatics
The lymphatic system plays a pivotal role in maintaining a low interstitial fluid volume and low interstitial protein concentration. Lymphatic flow is directly proportional to interstitial fluid pressure, meaning that any rise in interstitial hydrostatic pressure enhances lymphatic drainage and promotes the removal of excess fluid from the interstitium.
Lymphatics also clear proteins that escape through the capillary walls; without this removal, interstitial oncotic pressure would rise and favor edema formation.
Lymphatic vessels gradually merge into larger ducts—the right lymphatic duct and the thoracic duct—which ultimately drain into the subclavian veins, returning fluid and proteins to the systemic circulation.
