What is the Lymphatic System? - Structures, Function & Vocabulary

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  • 0:01 Lymphatic System
  • 0:34 Lymphatic Vessels
  • 2:14 Lymph Nodes
  • 3:07 Lymph Organs
  • 3:29 Spleen
  • 3:54 Thymus Gland
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Lesson Transcript
Instructor: Rebecca Gillaspy

Dr. Gillaspy has taught health science at University of Phoenix and Ashford University and has a degree from Palmer College of Chiropractic.

Your lymphatic system is an important part of your body's defense team. Learn about structures of the lymphatic system, such as the lymphatic vessels, spleen, thymus gland, tonsils and Peyer's patches, and the roles they play in keeping you healthy.

Lymphatic System

Your body is under attack. Every minute of every day, hostile germs try to make their way inside your body. Yet, most days you feel fine. This incredible ability to ward off invaders is the responsibility of your lymphatic system, which is a network of vessels, tissues and organs that help fight infection. In this lesson, you'll learn about the structures that make up the lymphatic system and how they work around the clock to keep you healthy.

Lymphatic Vessels

One important part of your lymphatic system is the network of lymphatic vessels that meander through your body. These vessels pick up and transport leaked fluids and return them to your bloodstream. What? You didn't know you had leaks inside your body? Well, it's true, but don't worry - the lymphatic vessels are an effective cleanup crew.

As you may know, blood is carried away from your heart by arteries. These arteries travel to every inch of your body, becoming smaller and smaller until they enter the smallest vessels of all, called capillary beds. Fluids are forced out of the arterial capillary beds and into the surrounding body tissues. Most of this leaked fluid is picked up by small veins known as venous capillary beds that channel blood back to your heart. The fluids that remain in the tissue spaces are picked up by your lymphatic vessels and are now referred to as lymph.

However, there's a problem. Lymph contains bacteria, viruses, cancer cells and other large particles that are normally too big to make it back into the venous capillaries. This contaminated lymph travels through progressively bigger vessels and is dumped back into your veins through two ducts: the right lymphatic duct and the thoracic duct. In other words, the lymphatic vessels carry potentially dangerous particles and give them a way to reenter your bloodstream. Thankfully, the other lymphatic tissues and organs jump in to help out.

Lymph Nodes

Lymph nodes are small cleanup stations positioned along the path of your lymphatic vessels. As lymph moves through your lymphatic vessels, it's channeled into small lymph nodes.

Bacteria, viruses and cancer cells found in the lymph are met by macrophages within your lymph nodes. If we break this word down into its two parts, we see that the prefix 'macro' means 'large' and the suffix 'phages' means 'eaters,' so macrophages are literally large eaters that have a big appetite for foreign materials.

Lymph is also met by lymphocytes within the lymph nodes. Lymphocytes are a type of white blood cell that help your immune system. Do you see the word 'lymph' hidden in this term? That's a good reminder that lymphocytes are cells that are important to the lymphatic system.

Lymph Organs

You have thousands of lymph nodes, and they do a good job of destroying foreign invaders, but they are not the only lymphatic tissue that is working for you. There are other lymphatic organs that provide additional levels of protection, including your spleen, thymus gland, tonsils and Peyer's patches. Let's take a look at each of these.


Your spleen is tucked up under your rib cage on the left side of your body, near the outer curve of your stomach. While your lymph nodes filter lymph, your spleen filters blood to remove bacteria, viruses and other foreign materials. In addition to acting like a filter, your spleen also makes lymphocytes, which is a function it shares with the lymph nodes and some other lymph organs.

Thymus Gland

Your thymus gland was very active when you were a child, but now that you're older, its purpose is on the decline. This gland is found in the upper part of your chest, just behind your breastbone. Your thymus gland produces a hormone called thymosin, which is needed for the production and maturation of T cells. T cells are specialized lymphocytes that destroy infected cells.

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