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| 16.23 | System: immune system | |
| The immune system defends the body from invading organisms that may cause disease. |
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| One part of the immune system uses barriers to protect the body from foreign substances. These barriers include the skin and the mucous membranes, which line all body cavities; and protective chemicals, such as enzymes in saliva and tears that destroy bacteria. | ||
| Another part of the immune system uses lymphocytes, specialized white blood cells that respond to specific types of foreign invaders. B lymphocytes produce proteins called antibodies, which circulate in the blood and attack specific disease-causing organisms. T lymphocytes attack invading organisms directly. | ||
| Let us now look at the human body sexual reproductive system. |
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