Final answer:
Lymphatic vessels draw lymph from the interstitial spaces between cells and transport it through an increasing network of vessels, which finally drains into the bloodstream via the subclavian veins. Lymph also contains immune cells and dietary lipids, and the system plays a crucial role in the immune system.
Step-by-step explanation:
The lymphatic vessels begin as open-ended capillaries that collect excess fluid, or lymph, from the interstitial spaces between cells. This network of vessels helps in transporting interstitial fluid back to the bloodstream. As lymph fluid accumulates, it is drawn into the tiny lymph capillaries and then moved through larger lymphatic vessels. Eventually, the lymph is transported into two large lymphatic ducts: the right lymphatic duct and the thoracic duct. These ducts then empty the lymph back into the bloodstream through the subclavian veins, which are located above the heart.
The lymphatic system also plays a key role in the immune system, transporting dietary lipids and immune cells. Immune cells, produced in the bone marrow, use the lymphatic system to travel throughout the body and congregate in primary and secondary lymphoid organs to mount immune responses. Lymph moves through the network of lymphatic vessels due to vessel contractions, movement by skeletal muscles, and the presence of valves that prevent backflow, ensuring it flows in one direction towards the veins just above the heart.