immune system organs and their functions

  immune system

Immune system is the primary defense center for living organisms. which works to protect them from exposure to many germs and microbes, that spread in the surrounding environment.  Which most of the time is the main cause of disease in living organisms.


immune system function

  • immune system is a collection of defense cells, which help expel unwanted bodies. 


  • Inside the body like harmful bacteria and causing germs , for diseases, infections and viruses. It causes , to spread to a group of conditions Sickness, including stubborn, and what is done fight it fast.


  • immune system functions as a whole system from cells and the vital processes that they carry out organs, cells, and particles within organisms live.  


  • The purpose of that is to overthrow diseases, toxins, viruses and cells of cancer, and foreign bodies that may take from the body a house to build its colonies.  That contribute to sabotaging the body’s processes natural or delayed.


  • This system identifies diseases and their pathogens, such as microbes or viruses, and exterminates them. 


  • A healthy immune system also distinguishes good cells and their vital tissues from foreign organisms that cause disease.


  • When functioning properly, the immune system identifies a variety of threats, including viruses, bacteria and parasites, and distinguishes them from healthy body tissues.


immunity definition

  • Immunity is the body’s natural ability to counteract disease-causing agents, such as viruses and bacteria that circulate in the human environment.


  • Where the body works to protect itself from diseases, and to protect it from infection.  Through a complex biological system that consists of a large number of cells, tissues and organs, which is the “immune system”.


  • Its primary function is to provide prevention and protection from invasive diseases that may enter the human body, causing fatigue and weakness.


  • immune system has the ability to destroy and get rid of viruses, bacteria or any foreign organisms on the human body.  Without causing any harm to the rest of the healthy body cells, in what is known as the “autoimmune response”.


 Components of the immune system

  • immune system is a complex system that pervades the body.  It is made up of a variety of cells that may move throughout the body, Or it may localize in a specific tissue.


  • Each of these cells has a unique role, and a different way, in identifying the problem, communicating with other cells, and performing their function.


  • But all immune cells originate in the bone marrow and later develop into adult cells through a series of stages, which occur in different parts of the body.  The immune system is represented by:


  1. 1) – organs 
  2. 2) – Cells 
  3. 3) – Proteins 


  •  1) – organs :

 Such as the skin, bone marrow, lymph nodes, some parts of the spleen, gut, thymus and tonsils.


  •  2) – Cells :

 Such as lymphocytes, basophils, eosinophils, neutrophils, and monocytes;  Which can differentiate into phagocytic cells (engulfing and digesting foreign bodies from the body) and natural killer cells.


  •  3) – Proteins :

 Like antibodies.

 components of the innate immune system





    Lymph nodes 









    Bone marrow






    Killer T cells 



    Temus or thymus



    White blood cells 






    Auxiliary chemicals group 






    Urinary Tract 


  •  Skin :

  The skin is the body’s first line of defense against microbes, and it produces some antimicrobial proteins.  In addition to the presence of some immune cells in the layers of the skin.


  •  Lymph nodes :

 Lymph nodes are small, bean-shaped structures that produce and store cells to attack disease.


 It is part of the lymphatic system that is made up of the bone marrow, spleen, thymus, and lymph nodes.


 Lymph nodes also contain lymph, which is the clear fluid that carries these cells to different parts of the body.  When the body fights an infection, lymph nodes can become swollen and painful.


  •  Tonsils :

 They are those two glands that specialize in working as guards in order to protect the body.  that from the entry of any foreign bodies or pathogenic microbes, which usually try to enter the body with the air or through food.


 The tonsils are located behind the mouth, and specifically on either side of the drooping soft palate.


  •   spleen :

 It forms the largest organ of the lymphatic system in the body and is located on the left side, under the ribs and above the stomach.  It contains white blood cells that fight infection or disease.


  •  Bone marrow :

 It is a yellow, spongy tissue found in the center of the bone that produces white blood cells. 


This tissue is found inside some bones, such as the thigh bone, and it contains stem cells, which are immature cells.


  •  Lymphocytes :

 Small white blood cells play a huge , role in the body’s defense against disease.


 There are two types of lymphocytes are B cells, which make antibodies that attack bacteria and toxins.  And T cells, which help destroy infected or cancerous cells.


 There are two types of lymphocytes; B cells and T cells.  B cells produce antibodies that attack bacteria and toxins.  T cells help destroy infected or cancerous cells.


  •  Killer T cells :

 It is a subset of T cells that kill cells infected with viruses and other pathogens. 


The T-cells help determine the immune responses that the body makes to a specific pathogen.


  •  Temus or thymus:

 Temus is a small organ where T cells mature.  It is located behind the sternum (it is in the shape of a leaf of thyme, hence the name). 


It can lead to the initiation or continued production of antibodies, resulting in muscle weakness (this is known as myasthenia gravis).


  •  White blood cells :

 These disease-fighting white blood cells identify and eliminate pathogens.


 It is the second line of defense for the natural immune system.  Leukocytes include phagocytes (macrophages, neutrophils, and dendritic cells), mast cells, eosinophils and basophils.


  •  Antibodies :

 Antibodies are produced by white blood cells, which are a chain of protein molecules.


 There are millions of different antibodies present in the blood, each of them sensitive to a specific pathogen. 


These molecules are synthesized in the liver and these proteins are activated by other cells of the white globules.


When a specific pathogen (bacteria, toxin or virus) is attacked, it causes it to degrade, swallow it, and then remove it.


  •  Auxiliary chemicals group :

 They are substances that help the immune system to do its job well and completely.


Among these chemicals, enzymes that kill microbes, in addition to interleukins, interferons, tears, saliva, and the mucous membrane.


  •  Hormones :

 There are many hormones that are secreted by the immune system and are generally called lymph hormones. 


 There are also hormones that suppress the immune system, the most famous of which is corticosteroids, so it is always recommended to take these compounds carefully and under medical supervision.


The hormone tymosin secreted by the thymus gland promotes the production of lymphocytes, a type of white blood cell.


There is the hormone interleukin, which are types secreted by white blood cells, which are many.


 There is interleukin 1, which is secreted by the phagocytic cells when a foreign body is swallowed (for example, a microbe). 


To work on its breakdown, this hormone has an interesting side effect, as it causes what is known as a fever “high body temperature”, and a feeling of fatigue, which is a way to kill some bacteria.


  •  Urinary Tract :

 It is one of the most important organs, and it has a high role to help the immune system perform its function. 


The reason for this is that it performs the final elimination of bacteria or microbes.  And that is by excreting urine out of the body.


immune system

 types of immunity

 immune system can be broadly classified into : 

  1. 1) – Natural or innate immunity 
  2.  2) – Acquired Immunity ex),
  •         A) – Active Immunity
  •    B) – passive immunity two types);  Maternal antibodies –


Immunoglobulin treatments

1) – Natural or innate immunity :

  • A type of natural immunity that is inherited or based on a genetic predisposition and denatured as genetic immunity. 


  • Natural immunity gives the body immunity and protection from birth to death. 


  • Innate immunity consists of external defenses (first line of defense such as skin), and internal defenses (second line of defense). 


  • Internal defenses include fever, supplement, natural killer cells, infections, balloon cells and interferons.


 Examples of natural or innate immunity:

  • A – Solid immunity that protects the body from incurable diseases, for a long time, as happens with German measles or mumps.


  • B – Short-term, transient immunity, which fights simple diseases that afflict the body, such as influenza.


  • C – permanent immunity that continues throughout life, such as the body’s immunity against the virus that causes polio.


 2) – Acquired Immunity :

  • Acquired or adaptive immunity is the body’s third line of defense. 


  • it is generated as a result of vaccinations and vaccinations, which are characterized by being long-lasting but slowly generated.


  • Adaptive or acquired immunity aims to attack specific threats to the body.


  • Acquired immunity is more complex than natural immunity.


  • In acquired immunity, the threat must be addressed and recognized by the body.  Then the immune system creates specially designed antibodies to this threat.


  • The acquired immunity may be either natural or synthetic.  Both natural and synthetic immunomodulators have passive and active components. 


  • Active immunity results from infection or immunization, while passive immunity comes from obtaining natural or artificial antibodies.


 A) – Active Immunity :

  • Active immunity is the most common type and develops with infection or vaccination.  These methods expose your immune system to bacteria or pathogens.


  • Immune cells called T cells and B cells realize that there is a pathogen – an invader – and activate the immune system to fight it.


  • The next time your immune cells encounter the same germs, they will recognize them, and instantly activate the rest of your immune system, to prevent you from getting sick.


 B) – passive immunity :

  • Passive immunity develops after receiving antibodies from someone, or from another location. 


  • This type of immunity is short-lived, because it does not stimulate your immune system to recognize the pathogen in the future.


 There are two important types of passive immunity :

 Maternal antibodies :

  • They are antibodies that are passed from mother to child. This usually occurs through the placenta or breast milk, especially in the first few days after birth.


 Immunoglobulin treatments:

  •  These are antibodies that are commonly used to treat people at risk of infection.


 How the immune system works pdf

 Through the above, we conclude how the immune system works :


  •  Natural Immunity:

It is a two-line, first line of defense and includes skin, sweat, earwax, tears, mucus in the respiratory passages, cilia, saliva, and stomach secretions (HCL acid).


  •  The second line of defense : includes the response to inflammation, interferons, and natural killer cells (NK).


  •  Acquired immunity (third line of defense):


 It includes immunity by antibodies, and immunity by intermediate cells (cellular immunity).


 immunity impact factor

Another division of immunity:

 1- Unspecified defenses :

  • These defenses work against all foreign substances and pathogens.


  • Examples include physical barriers, such as mucus, nose hair, eyelashes, and eyelashes.


  • Chemical barriers are also a type of indeterminate defense.  Examples of chemical barriers include lowering the pH of the skin, gastric juice, lysozyme in tears, the alkaline environment of the vagina, and earwax …


 2- Specific defenses:

  • This line of defenses activates against specific threats, such as bacteria, viruses, fungi, and prions ; (a term first used to describe the mysterious infectious agent responsible for many neurodegenerative diseases found in mammals), and mold. 


  • Usually the specific defense that acts against one pathogen is active against a different pathogen. 
  • An example of specific immunity is resistance to smallpox, from either exposure or a vaccine.


 Immune system features

 The immune system in the human body is characterized by :


  •  The speed in capturing any foreign objects on the human body, and working to exterminate them and prevent their spread at high speed.


  • Eliminate infected or damaged cells that may cause colonies to form.


  •  The superior ability to identify countless viruses and foreign bodies on the human body.


  • The immune system has defense mechanisms that protect the body from germs completely.


  • The immune system contains natural enzymes that protect the body from being infected by bacteria or viruses.