Lymph fluid comes from the intestines, where the digestive system produces a fluid called chyle, which is rich in proteins and fats. It also contains many immune cells, particularly lymphocytes, to attack any pathogens. Lymph fluid varies between white and clear in color.
Lymph fluid and the lymph vessels it travels through make up a crucial part of the immune system. The lymph fluid travels to and exudes from tissues all over the body. It carries threats such as cancer cells and organisms that cause disease with it from these tissues to the lymph nodes. The lymph nodes are small, soft structures located in several places throughout the body. They filter the lymph and release immune cells when harmful bacteria are present. The lymph system also includes the spleen, tonsils, adenoids and thymus.
Lymph vessels resemble veins in many ways and are closely associated with the vessels of the circulatory system. They rely on the incidental squeezing of surrounding voluntary muscles to move the lymph along. The presence of valves keeps the lymph fluid moving in the right direction. In addition to their immune function, lymph vessels also absorb excess fluids from the body's tissues and carry them to the bloodstream for excretion.