1. The lymphatic system is a network of very
fine vessels or tubes called lymphatics that drain
lymph from all over the body. Lymph is
composed of water, protein molecules, salts,
glucose, urea, lymphocytes, and other
substances.
Lymphatics are found in every part of the body
except the central nervous system. The major
parts of the system are the bone marrow,
spleen, thymus gland, lymph nodes, and the
tonsils. Other organs, including the heart, lungs,
intestines, liver, and skin also contain lymphatic
tissue.
The lymphatic system also helps defend the
body against invasion by disease-causing agents
such as viruses, bacteria, or fungi.