In vertebrates Parasitism

the dry skin of vertebrates such short-horned lizard prevents entry of many parasites.

the first line of defense against invading parasites in vertebrates physical barrier of tough , dry , waterproof skin, in reptiles, birds , mammals. microorganisms need moist environment survive. keeping skin dry, prevents invading organisms colonizing. human skin secretes sebum, toxic microorganisms. on other hand, larger parasites such trematodes detect chemicals produced skin locate hosts when enter water. saliva in vertebrate mouth prevents foreign organisms getting body orally. mouth contains lysozyme, enzyme found in tears , saliva. enzyme breaks down cell walls of invading microorganisms. should organism pass mouth, stomach hydrochloric acid, toxic microorganisms, next line of defense. intestinal parasites have thick, tough outer coating digested or not @ all, allowing parasite pass through stomach alive, @ point enter intestine , begin next stage of life. parasites can invade body through eyes. lashes on eyelids of mammals prevent microorganisms entering eye. tears contain enzyme lysozyme, kills invading microorganisms. once inside body, parasites must overcome immune system s serum proteins , pattern recognition receptors, intracellular , cellular, trigger adaptive immune system s lymphocytes such t cells , antibody-producing b cells. these have receptors recognize parasites.