the lymphatic system and immunity -...
TRANSCRIPT
The Lymphatic System and Immunity
Chapters 20 & 21
Objectives
1. SC.912.L.14.52 - Explain the basic functions of the human immune system, including specific and nonspecific immune response, vaccines, and antibiotics.
2. SC.912.L.14.42 - Describe the anatomy and physiology of the lymph system.
3. HE.912.C.1.3 - Evaluate how environment and personal health are interrelated.
Objectives
4. SC.912.L.14.6 - Explain the significance of genetic factors, environmental factors, and pathogenic agents to health from the perspectives of both individual and public health.
5. SC.912.L.16.10 - Evaluate the impact of biotechnology on the individual, society and the environment, including medical and ethical issues.
Functions
• Protects us against disease
• Respond to: – environmental pathogens
– toxins
– abnormal body cells, such as cancer
Pathogens
• Microscopic organisms that cause disease
• Ex: – viruses
– bacteria
– fungi
– parasites
Major Components
• Lymph – a fluid
• Lymphatic vessels
• Lymphoid tissues
• Lymphoid organs
• Lymphocytes – phagocytes
Major Components
• Spleen
• Thymus
• Lymphatic vessels
• Lymph nodes
• Tonsils
• Bone marrow
Lymphocyte Distribution
• Wander through tissues
• Enter blood vessels or lymphatics for transport
• Can survive many years
Lymphoid Tissues
• Dominated by lymphocytes
Lymph Nodes
• A filter – purifies lymph before
return to circulation
• Removes: – debris
– pathogens
– 99% of antigens
Thymus
• Deteriorates after puberty – diminishing effectiveness
• Site of T cell maturation
Spleen
• Removes abnormal blood cells/blood components
• Stores iron recycled from RBC’s
• Initiates B and T cell immune response
Lymphocytes
• Produced in lymphoid tissue, organs, and red bone marrow
• Function: – detect problems
– travel to an injury/infection site
• Travel in lymph through lymphatic vessels
Lymphocytes
• Make up ~20-30% of circulating leukocytes
• Most are stored, not circulating
• 3 classes: – T cells
– B cells
– NK cells
T cells
• Thymus dependent • ~80% of circulating lymphocytes • 3 main types:
– Cytotoxic T cells • attacks cells infected by viruses
– Suppressor T cells • inhibit function of T and B cells
– Helper T cells • stimulate function of T and B cells
B cells
• Bone marrow derived
• ~10-15% of circulating lymphocytes
• Produce and secrete antibodies – bind to specific antigens
– destroys a target
NK cells
• Natural killer cells
• ~5-10% of circulating lymphocytes
• Attack: – foreign cells
– virus-infected cells
– cancer cells
NK cells Tumor cell
Body Defenses
• Provide resistance to fight infection, illness, and disease
• 2 categories: – nonspecific defenses
– specific defenses
Nonspecific Defenses
• Always work the same way • Against any type of invading agent • 7 types:
– physical barriers – phagocytic cells – immunological surveillance – interferons – complement – inflammation – fever
Physical Barriers
• Keep hazardous materials outside the body
• Examples: – skin – mucous membranes – saliva – mucus – nasal hair – sweat – tears
Phagocytes
• Attack and remove dangerous microorganisms
• Examples: – microphages
– macrophages • engulf & destroy pathogens
• bind to pathogen so others can destroy it
• release toxic chemicals into interstitial fluid
Immunological Surveillance
• Constantly monitors normal tissues – NK cells
• ID and attach to abnormal cells (not selective)
• can attack cancer/viral-infected cells
Interferons
• Trigger production of antiviral proteins in normal cells – do not kill
viruses
– block replication in the cell
Complement (C) Proteins
• Form the complement system
• Complements actions of antibodies
Inflammation
• Triggers a complex inflammatory response
• Fever – accelerates defenses
– inhibits some viruses & bacteria
• Signs & symptoms: – swelling, redness, heat, pain
Specific Defenses
• Protect against specific pathogens
• Depend on activities of lymphocytes
• Specific resistance (immunity) – develops after exposure to environmental
hazards
Forms of Immunity
• Innate – present at birth
• Acquired – after birth
Acquired Immunity
• Active – antibodies develop after exposure to
antigen
• Passive – antibodies are transferred from another
source
Active Immunity
• Naturally acquired – through environmental
exposure to pathogens
• Induced – through vaccines
containing pathogens
Passive Immunity
• Naturally acquired – antibodies acquired
through the mother
• Induced – by an injection of
antibodies
Effects of Aging
• Immune system deteriorates – increased vulnerability to infections &
cancer
• T cells become less responsive to antigens
• Immune surveillance against tumor cells declines