Lymphatic system is one of the most important system of the body that carries the lymph fluid towards the heart. This system plays an important role in the body immune system.
The pressure in the lymph vessels are very low. The movement of adjacent tissue in the lymph is important to propel it through the lymphatics. The intrinsic or extrinsic compression are important for the lymph flow.
If you go on mc3.edu/admissions/applying-to-mccc/testing-and-assessment/assets/biology-placement-test.pdf page 11 it will tell you all the answers to your questions....