HOW IS THE IMMUNE SYSTEM MADE UP? - ANATOMY AND PHYSIOLOGY - 2025

The immune system is made up of a series of tissues, fluids and organs, among which the skin, bone marrow or blood stand out, among others. The immune system or immune system is the body's natural defense against external agents.

The body fights and destroys infectious agents that attack it before they do any damage. If the immune system works well, it protects the body from infections, and from the spread of diseases by viruses or bacteria.

There are two types of immune systems, the innate and the acquired. The innate immune system is present in all living beings and protects them against external aggressions. It can detect cells that pose a danger to the body.

The acquired immune system is found in vertebrates. They are more sophisticated defense mechanisms that adapt over time to recognize pathogens and attack them.

This process of recognizing pathogens is called immune memory. This creates a specific response to the specific pathogens that attack the body, improving the chances of success in killing it.

Components of the immune system

1- Skin

The skin is the main barrier of the immune system against the outside. It is the largest organ in the body and completely envelops it. Protects the body from external aggressions and helps maintain the body's structure.

The skin is divided into two parts, the dermis and the epidermis. The epidermis is the outer layer of the skin that is in contact with the environment.

The dermis is the inner part of the skin where the collagen and elastene fibers are found that keep the skin smooth.

2- Bone marrow

Bone marrow is the viscous tissue found within long bones such as the femur, vertebrae, ribs, sternum… The bone marrow is responsible for producing lymphocytes that are part of the immune system.

Furthermore, the bone marrow is one of the most important parts of the human body, as all blood cells are derived from cells located within the marrow.

Care must be taken not to confuse the bone marrow with the spinal cord, which is responsible for managing the sympathetic system and the body's impulses.

There are two types of bone marrow, the red and the yellow. Red bone marrow is responsible for creating blood and is found in flat bones such as the sternum, vertebrae, and ribs. The yellow bone marrow is found within the long bones and is an energy reserve.

3- Blood

It is the liquid connective tissue responsible for transporting the necessary nutrients to all parts of the body. Blood is made up of red blood cells, leukocytes or white blood cells, platelets, and plasma.

In addition to the transport of nutrients, the blood is also a defense against infections that threaten the body.

All blood cells are made in the bone marrow, which is found inside the bones.

4- scam

It is the lymphoid system of the immune system. The thymus is active during childhood and adolescence, and then over time it atrophies.

T lymphocytes are produced within this gland, which are responsible for shaping the immune response to external attacks on the immune system.

5- Lymphatic system

The lymphatic system is part of the circulatory system, and is responsible for transporting lymph. Lymph is the surplus that leaves the blood capillaries. It is a colorless liquid that runs through the lymphatic vessels made up of white blood cells and rich in protein.

Lymph collects interstitial fluid from the blood and defends the body from external pathogens.

6- spleen

The spleen is the organ in charge of eliminating old cells from the blood and forming new ones, in addition to maintaining the blood reserve. It is the center of the immune system and is part of the lymphatic system.

7- Mucosa

The mucosa is the protective layer of the organs, it is made up of the epithelium and the connective tissue that protects the walls of the internal organs.

How do the components act in the immune process?

When an infectious agent enters the body, the immune system recognizes it as a foreign agent and attempts to eliminate it. Foreign bodies that try to access the body are known as antigens.

These antigens can be of various types; a virus, such as the flu; a bacterium, trying to enter through an open wound, etc.

The immune system when it detects the antigen, sends the first line of battle to fight it, these are the macrophages.

These cells are found within the bloodstream in continuous movement to attack antigens as soon as they are detected.

When antigen enters the body and the macrophage detects it, it gets into a cell. When the antigen and macrophage are trapped within the cell, the macrophage begins to destroy the antigen by dividing it into small pieces called antigenic peptides.

If it is not a very strong antigen, this process would be enough to destroy it and eliminate it from the body. If, on the other hand, the antigen is stronger, this process is not enough and other parts of the immune system must intercede to kill the antigen.

If the macrophage process is not sufficient, the antigenic peptides bind to molecules called human leukocyte antigens (HLA). This binding causes molecules known as antigenic complexes that try to escape from the macrophage.

Once the antigen complex is released from the macrophage cell, the rest of the immune system can attack it. Class T lymphocytes can locate it once it is on the surface of the macrophage cell.

The lymphocytes then emit signals called cytokines that cause more T lymphocytes to travel to the site of the antigenic complex. This signal also alerts the B lymphocytes to produce antibodies.

The antibodies produced by B lymphocytes bind to the bloodstream to find the antigens in the body.

This helps prevent the antigen from reproducing or multiplying and concentrates it in one place in the body.

Finally, a cell known as a phagocyte is responsible for releasing the antigen from the body, expelling it to prevent the spread of the disease.

References

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