BIO 225 (Microbiology) CHAPTER OUTLINE
FOR HOST DEFENSE I FROM
MICROBIOLOGY FUNDAMENTALS A
CLINICAL APPROACH, COWAN SMITH
GREENE VILLE TECHNICAL COLLEGE
, Chapter 12: Host Defenses I (Nonspecific Defenses)
Defense Mechanisms of the Host: An Overview
Host defenses are a multilevel network of protections referred to as the first,
second, and third lines of defense.
First line of defense:
• What is the overall function? Includes any barrier that blocks invasion
at the portal of entry
• Very general in action
Second line of defense:
• Called innate immunity, is a more internal system of protective cells,
fluids, and processes that includes inflammation and phagocytosis
• Acts rapidly at both the local and systemic levels once the first line of
defense has been circumvented
Third line of defense:
• Acquired on an individual basis as each foreign substance is
encountered by lymphocytes
• The reaction with each different microbe produces unique protective
substances
• Provides long-term immunity
Most defenses overlap and are redundant in some of their effects. This
makes the survival of invading microbes unlikely.
First Line of Defense
Physical or Anatomical Barriers at the Body’s Surface
Skin:
• Why is intact skin the most effective physical barrier? It impedes the
entry of not only microbes but any foreign agent, whether living or not
• Stratum corneum
• How is sloughing of skin a protective feature? Takes associated
microbes with them
• Hair shaft is periodically shed and follicle cells are desquamated.
FOR HOST DEFENSE I FROM
MICROBIOLOGY FUNDAMENTALS A
CLINICAL APPROACH, COWAN SMITH
GREENE VILLE TECHNICAL COLLEGE
, Chapter 12: Host Defenses I (Nonspecific Defenses)
Defense Mechanisms of the Host: An Overview
Host defenses are a multilevel network of protections referred to as the first,
second, and third lines of defense.
First line of defense:
• What is the overall function? Includes any barrier that blocks invasion
at the portal of entry
• Very general in action
Second line of defense:
• Called innate immunity, is a more internal system of protective cells,
fluids, and processes that includes inflammation and phagocytosis
• Acts rapidly at both the local and systemic levels once the first line of
defense has been circumvented
Third line of defense:
• Acquired on an individual basis as each foreign substance is
encountered by lymphocytes
• The reaction with each different microbe produces unique protective
substances
• Provides long-term immunity
Most defenses overlap and are redundant in some of their effects. This
makes the survival of invading microbes unlikely.
First Line of Defense
Physical or Anatomical Barriers at the Body’s Surface
Skin:
• Why is intact skin the most effective physical barrier? It impedes the
entry of not only microbes but any foreign agent, whether living or not
• Stratum corneum
• How is sloughing of skin a protective feature? Takes associated
microbes with them
• Hair shaft is periodically shed and follicle cells are desquamated.
