Body Defenses  Body Defenses 2290 Photo by: Sebastian Kaulitzki
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Autoimmune diseases  Gamma globulin  Immune system    Lymph
nodes  Lymphatic system    Physical Barriers   Areas of the body
not covered with skin do not go unprotected. Mucous membranes,
the moist linings of the respiratory system, produce mucus
(MYOO-kus), a sticky substance that traps irritants that enter
through the nose. Structures like tiny hairs, called cilia (SIH-
lee-uh), line the body's airways and constantly wave foreign
particles and mucus away from the lungs to where they can be
swallowed safely. Most harmful microbes that make it to the
stomach are destroyed by stomach acids. In addition, tears and
saliva both contain enzymes that destroy invaders. Another
important defense mechanism is the brain-blood barrier, a
specialized "filter" that surrounds the brain and spinal cord
and acts as a physical barrier to keep out proteins, toxins, and
most microbes, while letting in glucose