Defense Mechanisms

Course Name


There are numerous disease-causing organism in our surroundings butthe body has effective systems to keep off the invaders

  1. Defending Mechanism-

They are categorized as either internal or external

2.1Internal barriers-

  1. Immune system- white blood cells and antibodies identifies harmful microorganisms and kill them by engulfing

2.2 Physical barrier-

  1. Skin – prevents entry of harmful microorganisms into the body

  2. Tears- lysozyme that kills bacteria invading the eye

  3. Mucous- contain secretions that fight invaders

  4. Membranes –keeps of invaders from reaching delicate body parts

  5. Earwax – keeps of dirt from reaching the ear drum

  6. Stomach hydrochloric acid – kills bacteria

  7. Urine – expels microorganisms from the urinary strip

  1. Conclusion

The body has very effective mechanism, both internal and externalthat keep off or kill invaders

Constantly, the human body experiences attacks from externalinvaders that tend to cause infections and diseases. The invadersexist in different forms ranging from microbes like fungi, viruses,and bacteria to non-living drugs, chemicals, and toxins. Despite theprevalence of disease causing organism and substances, the body hasseveral mechanisms that prevent the adverse effects caused by theseinvaders.

Defending Mechanisms

Physical barriers as well the immune system protect the body againstinvasion (Parham, 2014). The physical barriers include the skin,tears, mucous membranes, earwax and stomach hydrochloric acid. Inaddition, the normal flow of urine expels microorganisms from theurinary strip. The immunity system utilizes the white cells in theblood as well as antibodies to detect and destroy invaders that havepenetrated the physical barriers.

Unless damaged, the skin prevents entry of harmful microorganismsinto the body. Mucous membranes contain secretions that fightinvaders. For example, eye membranes contain tears with lysozyme thatkills bacteria invading the eye. Mucous in the airways filter dustparticles inhaled. Stomach acid, bile, pancreatic enzymes, and othersecretions kill invaders that enter the digestive system. The blood,as Parham (2014) explains also contains white blood cells andantibodies that identifies harmful microorganisms and kill them byengulfing. During an injury, inflammation occurs in the area andcauses the immune system to wall off the area, attack and killpotential invaders, dispose and repair the damaged tissue. The immunesystem is specific and produces substances that precisely attack theinvaders.


Naturally, the body fights diseases through physical barriers thatprevent invaders from entering the body. It also produces secretionsthat kill harmful microorganisms. The immune system detects anddestroys invaders that have crossed the physical barriers. Theinflammatory mechanism causes protection against infection duringtissue injury.


Parham, P. (2014). The immune system. Hamden: Garland Science.