The lymphatic system
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The Lymphatic System. Also Called the Immune System. Function of the Lymphatic System. The immune system is the body’s main defense against pathogens. The immune system recognizes, attacks, destroys, and “remembers” each type of pathogen that enters the body.

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The Lymphatic System

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The lymphatic system

The Lymphatic System

Also Called the Immune System


Function of the lymphatic system

Function of the Lymphatic System

  • The immune system is the body’s main defense against pathogens.

  • The immune system recognizes, attacks, destroys, and “remembers” each type of pathogen that enters the body.

  • Function of the Immune System: Fight infection through the production of cells that inactivate foreign substances or cells.


Organs in the lymphatic system

Organs in the Lymphatic System

  • Lymph nodes, lymph vessels, spleen, tonsils, and thymus gland


Nonspecific defenses

Nonspecific Defenses

  • First Line of Defense: Skin

  • Second Line of Defense: Inflammatory Response


Inflammatory response

Inflammatory Response

  • The inflammatory response is a nonspecific defense reaction to tissue damage caused by injury or infection.

  • When pathogens are detected, the immune system produces millions of white blood cells, which fight the infection.

  • Blood vessels near the infection expand, and white blood cells move from the vessels to enter the infected tissue.

  • May become painful and swollen.


Fever

Fever

  • The immune system also releases chemicals that increase the core body temperature.

  • The increased body temperature is advantageous because many pathogens can survive only within a narrow temperature range.

    • Slows down or stops the growth of such pathogens.

    • Also increases the heart rate so that the white blood cells can get to site of infection faster.


Specific responses

Specific Responses

  • If a pathogen is able to get past the body’s nonspecific defenses, the lymphatic system reacts with a series of specific defenses that attack the particular disease-causing agent.

    • These defenses are called the immune response.


The immune response

The Immune Response

  • A substance that triggers this immune response is known as an antigen.

    • Examples of Antigens: Bacteria, Viruses, and Other Pathogens.


Immune response

Immune Response

  • When a pathogen invades the body, its antigens are recognized by a small fraction of the body’s B cells…these cells then release antibodies.

    • Antibodies - Proteins that recognize and bind to antigens.

      • Carried in the bloodstream

      • As the antibodies overcome the infection, the plasma cells die out and stop producing antibodies.


Antibody structure

Antibody Structure

  • An antibody is shaped like the letter Y and has two identical antigen-binding sites.

  • Small differences in the amino acids affect the shapes of the binding sites.

    • The shape of the binding site makes it possible for the antibody to recognize a specific antigen with a complementary shape.

    • The different shapes give antibodies the ability to recognize a large variety of antigens.

    • A healthy adult can produce about 100 million different types of antibodies.


Acquired immunity

Acquired Immunity

  • The injection of a weakened or mild form of a pathogen to produce immunity is known as a vaccination.

  • Acquired immunity may develop as a result of:

    • Natural exposure to an antigen (fighting an infection)

    • Deliberate exposure to the antigen (through a vaccine).


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