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Pathophysiology-Body defense mechanism
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BODY DEFENSE MECHANISMCritical Thinking
Activity no. 2
1. Define and discuss the different types of body defense mechanism
The body has a defense mechanism to control and to protect against injury and
microorganisms. These defense mechanisms are:
● The skin and mucous membranes
Combination of physical and chemical barriers that prevents foreign agents from
penetrating the outer layer of the body.
a. Skin – cells filled with keratin makes the skin impenetrable, waterproof and
resistant to disruptive toxins and invaders. Dead cells are replaced, 1 million every
40 minutes. Sweat produced by glands in the skin wash away microbes and their
acidity slows bacterial growth.
b. Mucous Membranes – the inner surfaces of the body are guarded by mucous
membranes that line the respiratory, digestive, urinary and reproductive systems
and protect the internal lining, mucous membranes are more vulnerable than skin.
Its chemical barriers produce sticky mucus that traps microbes. Saliva and tears
contain enzyme lysozyme that kills bacteria by rupturing their walls
c. Hair in the nose acts as a filter. Cerumen protects the ear canal by trapping dirt
and dust.
● The mononuclear phagocyte system
, The monocytes are the largest of the white blood cells and constitute 3% to 8% of
the total blood leukocytes. Its circulating life span is three to four times, they also survive
for a longer time in tissues. These longer lived phagocytes help to destroy the causative
agent, aid in the signaling processes of specific immunity, and serve to resolve the
inflammatory process
Within 24 hours, mononuclear cells arrive at the inflammatory site, and by 48
hours, monocytes and macrophages are the predominant cell type. Macrophages engulf
larger quantities of foreign substances than the neutrophils. They also migrate to the local
lymph nodes to prime specific immunity.
1. Defensive Cells – play a role in inhibiting or destroying the pathogen before it harms
the body.
a. Phagocytes engulf pathogens, damaged tissue, or dead cells. Two types of
phagocytes are:
- Neutrophils - type of white blood cell in most people’s blood stream and
play a role in fighting many types of infection
- Macrophages – engulf infecting germs and infected cells.
b. Eosinophils are a type of disease fighting white blood cells that discharge
destructive enzymes to destroy pathogens too big for phagocytes. Example of
this is parasitic worms
Parasitic worms
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