Download Lymphatic and Immune System

Lymphatic and Immune System
The Body’s Defense
Nonspecific Defense
• First Line of
Defense
– Skin
– Mucous
Membrane
– Secretions
First Line of Defense
• This is a mechanical barrier that protects
the body from all types of pathogens
• Protective Chemicals
– Acid pH of skin secretions toxic to bacteria
– Stomach mucosa secretes HCl to kill
pathogens that are ingested
– Saliva contains lysozyme to kill bacteria
– Mucus traps microorganisms in digestive and
respiratory pathways
Nonspecific Defense
• Second line of
defense
– Phagocytic Cells
– Antimicrobial
proteins
– Inflammatory
Response
Second Line of Defense
• Cells and Chemicals
– Phagocytes like macrophages and neutrophils engulf
foreign particles and digest them with enzymes
– Natural Killer Cells are lymphocytes that lyse and kill
cancer cells and virus infected cells and act
spontaneously without need to “recognize” intruder,
they react to sugars on the cell surface and release
perforins to disintegrate the target cell’s membrane
– Inflammatory response which is triggered by tissue
injury
The Third Line of Defense
• Immune response
– Lymphocytes mediate
– Protective antibodies
– T cells (T
Lymphocytes)
• Act specifically and
directly (more about this
later)
4 Symptoms
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1. Redness
2. Heat
3. Swelling
4. Pain
• Sometimes
immobility is
included as a
fifth symptom
Inflammatory Response
• Chemical Alarm – Release Histamine and Kinins
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They cause blood vessels to dilate (Redness and Heat)
Capillaries to leak – (Swelling or Local Edema)
Activate pain receptors
Attract phagocytes and White Blood Cells
Movement may be impaired
• This prevents further damage to tissue
• Gets rid of cellular debris and pathogens
• Sets the stage for repair / forcing the person to rest
– Chemotaxis: cells follow chemical gradient
More on Inflammatory Response
• After 1 hour neutrophils arrive from bloodstream
through capillaries (Diapedesis)
• After 12 hours monocytes become macrophages
and that is when inflammation begins to subside
• Clotting proteins begin to wall off the area to
prevent spread of pathogens
• Fibrin mesh forms a scaffolding for repair
• Heat generated increases metabolic rate and
speeds up the healing process
Specific Defense
Immune System
• Third line of
defense
– Lymphocytes
– Antibodies
– Macrophages
Antimicrobial Chemicals
• Interferon
– Viruses take over a cell in
order to reproduce
– Cells that are infected secrete
proteins (interferon)
– This binds to nearby cells to
protect them from the virus
• Compliment Proteins
– 20 plasma proteins
– Activated when fixed to
fungi or foreign cells
– Binds to sugars like
antibodies on a cell
surface
– Put holes in target cell
surface
– Amplifies inflammatory
response
– Cause cell surfaces to
become sticky
(Opsonization)
Fever
• High body temperature
• Regulated by the
hypothalamus
• White Blood Cells secrete
Pyrogens
• Liver and spleen take up
iron and zinc to starve
bacteria
• Increases metabolic rate
to speed up repair
• High fevers =dangerous
Low grade = beneficial