What are the two basic structures that make up the lymphatic system?
Lymph vessels and lymph nodes. Lymph vessels carry the lymph, and lymph nodes clean the toxins from it.
The purpose of the lymphatic system is to carry a clear, whitish fluid called lymph from the extremities of the body, where it separates from blood, back to rejoin arteries in the neck. Lymph contains lymphocytes (a type of white blood cell), sugars, proteins, salts and fats. It does not contain red blood cells.
Lymph is carried through lymph vessels, which roughly resemble veins and arteries in their general anatomy. They are thin-walled and have valves, which prevent the lymph from flowing backwards - when a fluid flows the wrong way, it pushes the valves closed in front of it. They are also present in veins and arteries.
It also carries a lot of waste with it, such as from cells that die and produce toxic waste, or other waste from infection. This is cleared in kidney-shaped (but much smaller) structures called lymph nodes. They are located mostly around the neck, groin and axillae (armpits). Your tonsils are unusually large lymph nodes.