Function

The immune system is a collection of cells and organs that function to protect us from pathogens disease-causing organisms such as certain types of bacteria, protists, and viruses and toxins. There are three primary functions of the immune system:

  1. scavenge dead, dying body cells;
  2. destroy abnormalities (cancerous); and
  3. protect from pathogens and foreign molecules: parasites, bacteria, viruses.

As you read through this unit, you will see the word antigen used. An antigen is a foreign substance that triggers a reaction from the immune system. Antigens are often found on the surfaces of bacteria and viruses.

The lymphatic system is also part of the immune system with its network of vessels (see the model of this in Image 1- the green lines representing lymph vessels.), cells, and organs that carry and filter the excess fluids in tissues (or lymph) back to the bloodstream. This process filters pathogens from the blood.

Image 1

Question for thought:

What do the lymph vessels in Image 1 look like?

In summary:
The immune/lymphatic system defends against pathogens and toxins to protect the human body. This defense is carried out through processes such as:

    • activation and transportation of white blood cells A type of blood cell involved with an immune response also called leukocytes. and dendritic cells Cells that capture and present antigens as part of the immune response. to lymph nodes where immune responses are often triggered.
    • filtering of interstitial fluidAlso called tissue fluid, a solution that bathes and surrounds the cells. Produced from the leaking of plasma through the capillaries as blood is circulated through the body. as it returns it to the bloodstream.

CheckmarkCheck your understanding:

  • White blood cells are also called ___________.
  • A foreign substance that triggers a reaction from the immune system is termed ___________.
  • What is the role of dendritic cells in the immune system?
  • What system would respond to a pathogen?
  • How does the filtering of interstitial fluid play a role in the immune system?

 

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