A good story to remember how the lymphatic system protects the body from pathogens.
The white blood cells act as the body's military, the body is a huge battle ground. The war goes on forever. We are of course rooting for the WBC Army, but the Foreign Microbe Armies are impressive in their own right.
The WBC army bases are (where WBC's are produced) in the land of the Red Bone Marrow. These are well protected locations in large bones for the WBC to gather and plan their attack (sternum, long bones of the arms & legs, hip bones, scull, vertebrae). When they're ready and pass basic training they all take the Blood and Lymphatic Rivers to get anywhere in the world of the Body.
The WBC army has spies and scouts: chemicals that are released into Tissue Land from the invader microbes (pathogens). These chemicals signal the WBC's, telling them location, type of microbe, and the invaders numbers. Famous scouts are our brothers Histamine, Complement, Kinins and Leukotrienes. I always like to imagine microbes having a big loud obnoxious party after they pass the Great Skin Barrier (Body's first defense) and set up camp inside. They're jerks like that. They trash the neighborhood (damage nearby tissue).
Neutrophils are the first responders - the marines. They're tough and scrappy (they have granules in the cytoplasm and a multi-lobed nucleus). These guys are large in number - around 70% of the entire WBC army. They fight bacteria and fungal microbes the best. They show up early while the microbe invasion party is still going strong and begin to bust everything up. Acute inflammation is evidence of their fight. Pus litters the battlefield (a combo of dead neutrophils, microbes, and fluid and tissue from the area).
Next the Monocytes come and and clean up the area after the fight: "The Cleaners." They're different from the neutrophils - only 1 nucleus and no granules. They collect evidence of the invaders and send it to the T-cell division (lymphocytes who will remember the information for future attacks). After they're done in damaged Tissue Land they go back to the Lymphatic River. They can transform into macrophages.
Macrophages are big tanks that can kill larger microbes that have made it past the neutrophil battle. Like the monocyte, macrophages have a single nucleus. Marcrophages set up camps throughout the body waiting for any invader microbes that may have made it past enemy lines. They have different names for different camps throughout the body: ie Dust Cells in Lungs-ville, Kupffer cells in Liver-town. They like to set up road blocks in sinus cavities and lymph nodes where they can stop any microbes trying to get further past enemy lines.
Basophils, scrappy like the neutrophils (bi or tri lobed nucleus, full of granules) and show up and increase the inflamation. The bomb makers. They especially like to bomb allergies.
Eosinophils are also pretty scrappy like the neutrophils (bi-lobed nucleus and full of granules) and they arrive early to inhibit all the inflammation. The bomb squad maybe. They increase in numbers when the microbes are parasites or allergies because that's the fight they like to get in on.
A lymphocyte called the Natural Killer Cell helps out by recognizing human cells that have been invaded by viruses or tumor cells trying to establish bases past enemy lines. NK's are bad asses that notice the markers on the cells, then it kills the ones that indicate virus or tumor - no questions asked.
All these cells are part of the Innate Immune System - they're non-specific - they'll fight any pathogen that tries to set up shop. The Adaptive Immunity System is set up for repeat offenders. Remember the T-cell (friend of the monocyte) above? Along with the B-cell lymphocyte they remember pervious invaders and activate attacks accordingly. It's a big old war going on in there. All day, every day.
Using this analogy helped me meet most of the objectives of the lymph system. What a fun way to learn and teach this system!
