The Immune System

-The skin secretes antibacterial substances. These substances explain why you don't wake up in the morning with a layer of mold growing on your skin-most bacteria and spores that land on the skin die quickly

-Tears and mucus contain an enzyme (lysozyme) that breaks down the cell wall of many bacteria.

-Lymph nodes contain filtering tissue and a large number of lymph cells. When fighting certain bacterial infections, the lymph nodes swell with bacteria and the cells fighting the bacteria, to the point where you can actually feel them. Swollen lymph nodes may therefore be a good indication that you have an infection of some sort.