Summary Human Physiology and Anatomy: The Immune System

Immune System:
- All the times we are surrounded by microbes.


Types of Immune System Defense Mechanisms:
 Non-Specific Defense Mechanisms (Innate Immunity)
o Innate Immune System: cells and proteins are always there to fight infection.
 Triggered by a wide range of threats
 First line of defense in the body always ready and prepared to defend
 Defense at body surfaces (skin)
 Phagocytosis (leukocytes)
 Natural antimicrobial substances (Saliva, lysozymes, HCl),
tears, and cilia.
 Second line of defense against invasion
 Inflammatory response


 Specific Defense Mechanisms (Adaptive Immunity)
o Adaptive Immune System: comes into action against pathogens that are able to
overcome the innate immune system
 Directed against antigen (antigen-specific)
 T & B cells: recognize antigens
 Bacteria
 Viruses
 Parasites
 Memory


The Inflammatory Response:
Causes:
 Microbes
 Physical changes (mechanical injury, heat)
 Chemical agents
 Microbial toxins
 Organic poisons
 Inorganic agents (acid)

, Signs:
 Redness
 Heat
 Pain
 Swelling


Steps for inflammatory response:
1. Mast cells release histamine: vasodilation and increase blood flow
2. Macrophages (monocytes) and neutrophils: engulf pathogens
3. Blood clotting prevent blood loss
4. Excess fluid in the injured area presses on nerve endings which then release
“bradykinin” causing pain




 Acute Inflammatory Response: is beneficial as it removes harmful agents and allows
for healing (high Neutrophils and Monocytes)
 Chronic Inflammation: high lymphocytes


Specific Defense Mechanisms (Adaptive Immunity):
- Take place when a nonspecific response fails to overcome the infection
- The immune response is directed against only one antigen