The immune device (from the Latin word immunis, meaning: "free" or "untouched") is the body defense system. The is made up of a network the cells, tissues and also organs that all occupational together to protect us versus pathogens (disease-causing microorganisms, such together viruses, bacteria, parasites and fungi). Pathogens cause infection as soon as they get in the body and also begin to multiply. Condition occurs when your body’s cells room damaged since of the infection. Then signs and symptoms of illness appear.

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Cells, organs and also tissues of the immune system

The cells, organs and tissues that the immune device are situated throughout the body, enabling for a quick solution to infection. Study the image below from the Vaccine equipments Project to find out what organs and also tissues are component of the immune system and where they room located.


White blood cell (also referred to as leukocytes) are the cells of the immune system. They space responsible because that protecting the body versus pathogens. They are developed in the bone marrow and stored in several places throughout the body, consisting of the thymus, spleen and also lymph nodes. They take trip throughout the human body via the bloodstream and in specialized vessels called lymphatic vessels.

There are several species of white blood cells, all with details functions. Examples include phagocytes (like macrophages) the roam the body looking for any foreign invaders to destroy and also lymphocytes (B cells and also T cells) the are set into activity in an answer to a specific pathogen such together a virus or bacterium. When a virus is recognize the different species of white blood cells work together to acknowledge it and also respond, protecting the human body from disease.

The immune system has actually two key parts: Innate and also Adaptive

The immune system has actually two key parts, the inherent immune system and also the adaptive immune system. 


The inherent Immune System

The natural immune system is our body’s first line that defense versus pathogens. That is a generalized, non-specific defense mechanism (meaning the the defenses protect versus all pathogens).

The inherent immune mechanism defenses consist of the protective mechanisms we space born with (innate method “inborn” or “natural”). These encompass physical barriers like our skin and mucous membranes, chemical obstacles like saliva and also stomach acid, immune system cells like macrophages that space constantly top top the lookout for pathogens come destroy, proteins like cytokines (chemical messengers the immune cells usage to communicate with one another), and also the inflammatory solution (inflammation). In most situations the natural immune defenses are enough to fight turn off pathogens before they can cause an infection however when castle aren’t, the adaptive immune mechanism is referred to as into activity (the adaptive immune system is spanned in the next lesson).

Watch the video from Crash food to learn more about the innate immune mechanism (the video below will only show friend the best parts, yet feel complimentary to watch the whole thing if you"d like!).



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The Adaptive Immune System

The adaptive immune system (adaptive meaning it have the right to adapt come a particular threat) is the body’s second line of defense versus pathogens. The is a specific defense system (meaning that its defense mechanisms directly target a specific pathogen) that is called into activity when natural defenses room overcome. The specificity of the adaptive immune system originates from its capability to identify a pathogen by its antigens. Antigens are molecule structures, such together proteins or polysaccharides (complex sugars) discovered on the surface ar of a pathogen, that space able to cause the immune system to respond.

The key cells the the adaptive immune system are B cells and T cells. If a microorganism invades the body, it is detected by an antigen-presenting cell, such as a dendritic cell. This cells display antigens from the microorganism on their cell surface and also travel come the lymph nodes where they current the antigen come T cells, activating them. This T cells then activate B cells to produce Y-shaped protein called antibodies that connect to the pathogen and one of two people neutralize it (by preventing it from entering various other cells), or tag it for various other immune cell to destroy. Various other T cells are able to damage cells that have already been infected. Some T cells and also B cell become memory cells that protect against infection in the future. If the same microorganism invades the body again, these cells mental it and also respond quickly and also efficiently, staying clear of infection. This security is called immunity.

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Watch the video clip from Crash course to learn more about the adaptive immune system (the video below will only show girlfriend the finest parts, yet feel free to watch the entirety thing if you"d like!).