What Are the Organs of the Immune System?

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  • 0:03 Immune System
  • 0:37 Primary Organs: Bone…
  • 1:37 Secondary: Skin, Lymph…
  • 3:23 Other Secondary:…
  • 4:21 Lesson Summary
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Lesson Transcript
Instructor: Amanda Robb
In this lesson, we'll cover both the primary and secondary organs of the immune system. Specifically, we'll look at the function of each and how they work together throughout our life to protect our body against invaders.

Immune System

Behind the scenes, a war rages on inside your body. The enemy is closing in and soldiers are falling left and right. Whenever you have a stuffy nose or a sore throat, you can picture this scene happening inside your body. The enemy is a pathogen, or an infectious particle like a virus or bacteria, and your soldiers are the immune system. Your immune system is a collection of organs, tissues and cells that fight off pathogens. Today, we'll learn about two classes of organs in your immune system; primary and secondary organs.

Primary Organs: Bone Marrow & Thymus

Primary immune organs are where the immune cells are made. These organs are crucial for creating an immune system when you are born. Bone marrow, a soft tissue inside your bones, is the birthplace of all your blood cells, including your white blood cells, or lymphocytes, which are the main fighters in your immune system. Lymphocytes track down invaders, killing them and alerting your body when you are under attack.

The thymus, an immune organ responsible for developing immunity, is only working at full capacity during childhood. The thymus specifically cultivates T-cells, which find both pathogens and infected host cells to destroy them. In children, the T-cells circulate into the thymus, which is like a school for the T-cells. In the thymus, T-cells learn to recognize what types of cells are self and what cells are invaders. If the T-cells don't mature properly, a person can develop autoimmune diseases where the T-cells attack the body instead of pathogens.

Secondary Organs: Skin, Lymph Nodes, & Spleen

Secondary immune organs are where the lymphocytes do their job. Lymphocytes circulate to these organs to fight off invaders. Your skin and mucus membranes, like your nasal passage, are the first barrier of defense in your immune system. We typically think of the skin as a physical barrier to stop entry of bacteria, but the skin is also filled with both immune cells and chemicals that defend against pathogens.

Throughout the day, fluid accumulates in your tissues from your blood vessels. The lymphatic system is a collection of tubes that bring that fluid back to the heart, where it goes back into the blood vessels. White blood cells circulate in the lymphatic system. As the excess fluid flows into the tubes, white blood cells check for invaders. The lymph fluid also flows through a series of checkpoints called lymph nodes. These are like filtering stations for the blood that contain a high number of lymphocytes that can screen for pathogens.

You can check out your lymph nodes in action when you're sick. If you feel around your neck, you might feel two bumps. These are your lymph nodes. You have lots in your body, but these are easy to access. If they are swollen and large, it's a sure sign you have an infection. When your body is fighting off a pathogen, the lymph nodes become inflamed, taking on extra blood and working overtime to get rid of it.

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