Lymph Nodes: Anatomy & Location

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  • 0:01 What Is a Lymph Node?
  • 0:54 Anatomy
  • 2:06 Lymph Node Function
  • 3:40 Where Are Lymph Nodes?
  • 4:09 Lymph Node Activation
  • 5:24 Lesson Summary
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Lesson Transcript
Instructor: Stephen Christensen
This lesson will help you understand the anatomy and function of lymph nodes, and you will learn where lymph nodes are located in your body. A quiz at the end of the lesson will test your knowledge.

What Is a Lymph Node?

If you've ever had a case of strep throat or mono, you probably remember feeling swollen lymph nodes, sometimes called glands, in your neck below your jaw. If you use your fingertips to gently probe your neck, armpits, or groin area, you may be able to feel lymph nodes even when you're healthy. Lymph nodes feel like rubbery beans or peas beneath the skin. A lymph node is a small, bean-shaped organ that serves as a filtering and processing center for your immune system. Approximately 600 lymph nodes are scattered throughout the human body. They can exist singly or in closely connected groups called chains. Lymph nodes are connected to their neighbors by a sort of network of tubes called lymphatic vessels.


From the outside, a lymph node looks like a fat lima bean: it is oval in shape, and has a small indentation called the hilum on one side. The lymph node is covered by a tough capsule, which is penetrated in multiple places by lymphatic vessels.

The lymphatic vessels carry lymph, a clear liquid containing white blood cells, proteins, salts, and water, into and out of the lymph node. Lymphatic vessels have one-way valves along their inner walls to help move lymph in the right direction. As lymph moves past a valve, the valve closes like a door and prevents the lymph from moving backward.

The inside of a lymph node is divided into several chambers by wall-like structures called trabeculae. Stretched between the trabeculae is a meshwork of thinner walls called reticular fibers. Together, the trabeculae and reticular fibers form a support network for immune cells that are packed in like grapes. Throughout the lymph node's interior are a series of street-like channels called sinuses that help guide the flow of lymph.

Lymph Node Function

Lymph is formed from fluid that leaks from your blood vessels. Your body re-captures this fluid in lymphatic vessels, channels it through your lymph nodes, and eventually returns it to your bloodstream. The lymph flowing in a lymph node carries with it the bacteria, viruses, cancer cells, debris, and other potentially dangerous agents that have filtered into the lymphatic vessels from your bloodstream and tissues.

Lymph enters a lymph node through an afferent lymphatic vessel and exits through an efferent lymphatic vessel. Think of the e in exit and the e in efferent to remember which is which. As the lymph filters through the node, any infectious organisms or cancerous cells within the lymph are trapped by the reticular fibers, where they can be detected by the node's immune cells. Since there are fewer efferent, exit lymphatic vessels than afferent, enter, vessels, the flow of lymph is slowed within the lymph node. This gives the immune cells time to accomplish their protective functions.

The white blood cells within the lymph node have several functions. Some produce antibodies that destroy infectious organisms; others eliminate abnormal cells, such as cancer cells, and mature lymphocytes act as 'teachers' for immature lymphocytes. When the lymph finally leaves the node, through an efferent lymphatic vessel it carries antibodies and other immune molecules, as well as other educated immune cells that can mobilize an immune response throughout your body.

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