Parts of the Human Immune System

The world is a hostile place, with some of our worst enemies existing at a microscopic level. A vigorous immune system is key to fighting off these tiny adversaries, which our body does with a variety of cells and organs that compose our immune and lymphatic systems. Here’s a look at some of the most important parts of the human immune system.

Bone Marrow

When it comes to the immune system, it all begins in the bones. Bone marrow, the spongy material located inside bones, is your body’s producer of blood cells, both red and white. White blood cells, or leukocytes, make up most of the immune system, attacking pathogens and forming antibodies. Most bone marrow shifts from red to yellow as you age, but it retains its key role in the immune system.

Lymph Nodes

The lymph nodes, located throughout the body, also contribute to white blood cell production by producing lymphocytes, which not only fight off invaders but leave memory cells so that the body can recognize and fight familiar foes. The lymph nodes also filter lymphatic fluid, which travels alongside blood and presents the antigens that lymphocytes attack.

Tonsils

You may not know it because yours were removed so early, but the tonsils serve an important purpose in your body’s immune system. The tonsils use their position in the mouth to fight off airborne and foodborne pathogens that enter through the mouth by identifying invaders and producing antibodies. Unfortunately, it is this front-line duty that costs so many of us our tonsils: the inflammation they bear from catching pathogens often ends up calling for their removal.

Mucous Membranes

Mucous membranes are also found throughout the body, such as in the nose, mouth, lips, and ears. These membranes secrete mucus, which serves not only to keep surfaces hydrated but also to capture invasive pathogens and particles and flush them from the body before they can cause infection.

Thymus

Behind the sternum, or breastbone, lies the thymus, a specialized organ of the immune system charged with the maturation of T cells. Thymocytes produced in the bone marrow are not immediately ready to work as part of the immune system. Upon migration to the thymus, they are processed and developed in what amounts to a cellular training session. The thymus is its most active in children, and as the body matures and the organ has produced sufficient T cells, the thymus is slowly replaced by fatty tissue in puberty and adulthood. 

Spleen

The spleen is a large lymphatic organ that filters the blood similar to how lymph nodes filter lymph. Like the tonsils, the spleen is susceptible to heavy inflammation, and in some cases, may even rupture. A ruptured spleen often necessitates surgical removal, which will require patients to receive vaccinations that compensate for the lost immunological function, underscoring its importance among parts of the human immune system.

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