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physical & humoral defense mechanisms
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Brain-Blood Barrier
Lines of defense your body puts up
physical & humoral defense mechanisms
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, the source of the brain's nutrients.
Skin
Tears, stomach acids, and sweat.
Acids in the stomach destroy pathogens that are swallowed. Tears and saliva both contain enzymes that destroy invaders. Lysozymes in tears destroy pathogens on the surface of the eye. Salt in sweat also kills bacteria, and interferon in blood blocks viruses from infecting cells.
Skin, the largest body organ, provides both a physical and a chemical barrier against the outside world. The skin forms a protective layer that completely wraps around the body, shielding blood vessels, nerves, muscles, organs, and bones. When cuts or tears in the surface of the skin provide an entrance for infective agents, glands beneath the skin produce an enzyme that helps kill bacteria.
Mucous membranes
Mucous membranes, the moist linings of the respiratory system, produce mucus, 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.
Fungi
are microorganisms that can grow in or on the body, causing infections of internal organs or of the skin, hair, and nails.
Physical Mechanisms
The covering of the body (skin) and the lining of the tubes of the body (mucous membranes) provide mechanical barriers against pathogens. Tears, stomach acids and sweat provide a chemical barrier against pathogens. Fever causes the liver and spleen to take iron out of the bloodstream.
what organisms seek to harm us?
Parasites
Humoral defense mechanisms
are organisms such as protozoa (one-celled animals), worms, or insects that must live on or inside a human or other organism to survive. An animal or plant harboring a parasite is called its host. Parasites live at the expense of the host and may cause illness.
An indirect form of attack that employs antibodies produced by plasma cells, which have been developed from B cells. The antibodies bind to an antigen and thus tag them for destruction.