Immune/Lymphatic System Immune System Functions: ● Body’s main defense against pathogens (disease causing agents) ● Recognizes, attacks, destroys and “remembers” each type of pathogen that enters the body ● Resistance of an organism to infection, disease, or other unwanted biological invasion (pathogens)— this process is called immunity Defense Mechanisms: ● Skin—keeps pathogens out of body--pathogens can only enter and multiply where skin is broken ● Mucus, saliva, tears, oil and sweat contain chemicals that kill bacteria ● Mucus in throat traps pathogens ● Acid and digestive enzymes in stomach destroy pathogens ● If pathogens do enter body they multiply quickly and release toxins ● Inflammation—millions of white blood cells are produced to engulf and destroy pathogens (pus and swelling) ● Body produces chemicals that cause fever—increased body temperature slows down or stops growth of bacteria ● Antigens—identifying molecule on surface of pathogens (specific) ● B-cells and T-cells recognize specific antigens and respond to them in order to destroy the pathogen ● Antibodies are proteins carried in the bloodstream that are produced to recognize and bind to specific antigens in order to stop infections ● Injection of a weakened form of a pathogen to produce immunity is known as a vaccination (vaccine) Lymphatic System: ● Plays a critical role in the immune system by producing, storing, and circulating white blood cells ● Collects fluid lost by the blood and returns it to the circulatory system ● Network of vessels and associated organs o lymph – fluid in lymph vessels o lymph vessel s – move the lymph throughout the body o lymph nodes -- act as filters to trap bacteria and other organisms that cause disease ● Tonsils, thymus and spleen are all composed of lymphoid tissue ● tonsils – filter and destroy bacteria ● thymus – produces hormones that aid in maturation of white blood cells ● spleen – removes worn-out red blood cells, platelets, bacteria from the blood Comparative Immune Systems: The immune system is well developed and is very complex in mammals and higher forms of vertebrates. The complexity of the immune system decreases as we go down the evolutionary scale. Organisms such as birds, reptiles, amphibians, fish, etc. have comparatively simple types of immune systems. There is no immune system in invertebrates such as starfish, jellyfish, earthworms, insects, etc..