THE DEFENCE SYSTEMS OF THE BODY
The defensive mechanism is an inborn instinct of a living organism it has a priority at every stage ranging from an individual human to society state and even at the national level human body also has a well organised defence system there are two types of defence mechanisms in the body (1) Non-specific defence and (2) Specific defence
Non-specific defence mechanism preventing the entry of microbes or other foreign material::
The body s first line of defence against foreign invaders is the tough outer layer of skin that forms a physical barrier to the entrance at microbes (for details refer chapter 18) Mucous-membranes lining the mouth gut and respiratory passages also provide protection by inhibiting the entrance of microbes the mucous secreted there traps the microbes similarly cilia alongwith mucous also trap and remove microbes hair present in nose filter microbes and dust tears from the lachrimal apparatus at an eye dilute and wash away irritating substances and microbes similarly saliva from salivary glands washes microbes from surfaces at tooth and mucous membrane in the mouth even the epiglottis prevents microbes and dust from entering the trachea
In addition to above mentioned boundries for foreign substances certain chemical substances secreted at various parts of entry destroy or discourage growth of microbes they are gastric acid and other gastric secretions acidic pH of skin unsaturated fatty acids in sebum and lysozymes in perspiration (sweat) tears saliva nasal secretions and tissue fluids finally the normal microflora of the gut also help to suppress the growth of more virulent micro-organisms
Even if microbes enter the body cells there are some other non-specific defence mechanisms that try to destroy microbes increase in body temperature (fever) inhibits microbial growth and speeds up body reactions that aid repair white blood cells by the mechanism of phagocytosis try to engulf microbes or foreign invaders reticulo-endothelial-system (RES) is one of the most important system involved in protecting the body from foreign invaders lastly inflammation is a physiological defence mechanism involved in protecting the body from the injury caused by microbes or foreign material moreover fever inflammation interferon etc are also non -specific defense mechanisms
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