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Our immune mechanism is consisted of of both individual cells and proteins and also entire organs and organ systems. The offal of the immune system incorporate skin and mucous membranes, and also the guts of the lymphatic device too.

Organs that duty as barriers

Your skin and mucous membranes room the very first line of defense versus germs entering from outside the body. Lock act as a physical obstacle with assistance from the following:


Primary lymphoid organs: these organs include the bone marrow and also the thymus. They develop special immune system cells dubbed lymphocytes.
Secondary lymphoid organs: these organs encompass the lymph nodes, the spleen, the tonsils and specific tissue in miscellaneous mucous membrane great in the human body (for circumstances in the bowel). It is in these organs whereby the cells of the immune device do their actual task of fighting turn off germs and also foreign substances.

Bone marrow

Bone marrow is a sponge-like tissue uncovered inside the bones. The is where most immune device cells are produced and also then likewise multiply. These cells relocate to other organs and tissues through the blood. At birth, countless bones contain red bone marrow, which proactively creates immune system cells. Over the food of our life, an ext and more red bone marrow turns right into fatty tissue. In adulthood, only a few of our bones tho contain red bone marrow, including the ribs, breastbone and also the pelvis.


The thymus is situated behind the breastbone above the heart. This gland-like organ reaches full maturity just in children, and is then progressively transformed to fat tissue. Special types of immune mechanism cells referred to as thymus cell lymphocytes (T cells) tires in the thymus. Among other tasks, this cells coordinate the processes of the innate and adaptive immune systems. T cells move through the body and also constantly screen the surface of all cells for changes.

Lymph nodes

Lymph nodes are small bean-shaped tissues found along the lymphatic vessels. The lymph nodes act as filters. Miscellaneous immune mechanism cells catch germs in the lymph nodes and activate the creation of unique antibodies in the blood. Puffy or pains lymph nodes are a sign that the immune mechanism is active, for example to fight an infection.


The spleen is located in the left top abdomen, in ~ the diaphragm, and also is responsible for various kinds the jobs:

It stores various immune mechanism cells. When needed, they relocate through the blood to various other organs. Scavenger cells (phagocytes) in the spleen act together a filter for germs that gain into the bloodstream.
It stores and also breaks under platelets (thrombocytes), which room responsible because that the coagulation of blood, among other things.

There is always a lot of blood flowing through the spleen tissue. At the same time this tissue is really soft. In the event of significant injury, for example in an accident, the spleen may rupture easily. Surgery is then typically necessary because otherwise over there is a peril of bleeding come death. If the spleen demands to be eliminated completely, various other immune system organs can lug out that is roles.


The tonsils room also component of the immune system. Since of their place at the throat and palate, they can stop germs entering the body through the mouth or the nose. The tonsils likewise contain a the majority of white blood cells, which are responsible for killing germs. There room different species of tonsils: palatine tonsils, adenoids and also the lingual tonsil. Every one of these tonsillar frameworks together are sometimes referred to as Waldeyer"s ring due to the fact that they type a ring approximately the opened to the neck from the mouth and nose.

There is also lymphatic organization on the next of the throat, which have the right to perform the features of the palatine tonsils if they space removed.

Mucous membranes

The bowel plays a central role in defending the body versus germs: an ext than fifty percent of all the body"s cell that produce antibodies are discovered in the bowel wall, especially in the last component of the tiny bowel and also in the appendix. This cells detect foreign substances, and also then mark and destroy them. They also save information about the substances in stimulate to have the ability to react more quickly the following time. The huge bowel additionally contains not authorised bacteria dubbed gastrointestinal or gut flora. Healthy gut flora do it complicated for virus to spread and enter the body.

Mucous membranes assistance the immune device in other parts of the body, too, such as the respiratory and urinary tracts, and also the lining of the vagina. The immune system cells are straight beneath the mucous membranes, where they protect against bacteria and viruses indigenous attaching.

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Brandes R, Lang F, Schmidt R (Ed). Physiologie des Menschen: mit Pathophysiologie. Berlin: Springer; 2019.