The lymphatic system performs three main functions, states the National Cancer Institute. The system absorbs and transports fats and fat-soluble vitamins, drains excess fluid from body tissues to the blood and aids the body's immune system by filtering out harmful microorganisms from lymph.
The lymphatic system contains lymphatic organs, lymphatic vessels and lymph, notes the National Cancer Institute. Lymphatic organs are typically composed of clumps of lymphocytes and other cells arranged within a network of connective tissue and include the thymus, tonsils, spleen and lymph nodes. Lymphocytes are a critical part of the body's immune response.
The other primary component of the lymphatic system, the lymphatic vessels, is restricted to transporting fluid away from body tissues, notes the National Cancer Institute. The smallest of these vessels, lymph capillaries, are rooted in the interstitial spaces that collect fluid. The walls of lymphatic capillaries act in a similar manner to valves, allowing fluid ingress while preventing lymph flowing out. These capillaries are found throughout the body with the exception of tissues that lack blood vessels, such as the central nervous system.
Lymph, the final primary component of the lymphatic system, has a similar composition to blood plasma, notes the National Cancer Institute. Lymph collects in interstitial spaces as fluids pass through capillary walls. The accumulated fluid is transported away from these spaces and back to the blood by lymph capillaries. This process prevents fluid accumulation, a condition known as edema, and helps regulate blood pressure and volume.