Answer:
Lymph nodes
Step-by-step explanation:
The interstitial fluid is used by cell for material exchange and present between the cells is collected by lymph vessels called as lymph. These vessels are designed so that the interstitial fluid can enter the vessel but the lymph can't exit from it. The lymph circulate throughout the body through these lymph vessels.
There are checkpoints in lymphatic system containing the white blood cells and present in various areas of body for the filtration of lymph are known as lymph nodes. It is kidney shaped organ and present in adaptive immune system. The major lymph nodes are located in above the colborne, in the armpits, tonsils, adenoid and on either side of neck linked to lymph vessels. These lymph nodes contain the macrophages which are phagocytic cells and when the lymph passes through the lymph nodes they act as military checkpoint and capture the diseased cells, cellular debris, bacteria and viruses. Infected cell such as cancer cells are captured by them and the particular lymph become swollen by the response such lymph nodes become swollen in upper respiratory infection.