The Lymphatic System
Lymph vessels return fluid to the blood and house immune cells.
About this topic
The lymphatic system is a network of vessels, nodes and organs. It collects excess tissue fluid that leaks from capillaries and returns it to the blood as lymph, absorbs fats from the intestines via lacteals, and is a key part of immunity. Lymph nodes filter pathogens and contain white blood cells.
Blood pressure forces some fluid out of capillaries, bathing cells. Most returns to the blood, but the rest enters lymph capillaries and flows through larger vessels, moved by muscle contraction and one-way valves, since there is no pump like the heart. The lymph eventually drains into veins near the heart.
When you have an infection, the lymph nodes in your neck or armpits can swell and feel tender because lymphocytes are multiplying to fight pathogens. Other lymphatic organs include the spleen, which filters blood, the thymus, where T cells mature, and the tonsils. Fats absorbed in the villi enter the lacteals and reach the blood through lymph.
If lymph drainage is blocked, fluid builds up, causing swelling called oedema. Cancer can spread through lymph nodes, which is why doctors check them. A common misconception is that lymph is a different fluid from blood; it is derived from blood plasma and is mostly clear.
Key ideas
- Lymph nodes filter pathogens
- Swollen glands show infection
- Fluid leaks from capillaries
Quick check
Use cases: where The Lymphatic System helps
- Homework: review the key idea behind The Lymphatic System before you start a problem set.
- Exam revision: use the quick check to test whether you can recall The Lymphatic System without notes.
- Visual learning: play with the interactive lab to see how The Lymphatic System changes when you adjust its inputs.
- Teaching a friend: explain The Lymphatic System in your own words, then compare your version with the key ideas.
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Frequently asked questions
What is The Lymphatic System?
Lymph vessels return fluid to the blood and house immune cells.
What will I learn in The Lymphatic System?
Lymph nodes filter pathogens. Swollen glands show infection. Fluid leaks from capillaries.
Is The Lymphatic System part of Biology?
Yes. It is one of 150 Biology topics on LearnViz HighSchoolEdu, with 3 key ideas, a live animation and a quick check.
Does the The Lymphatic System lab work on a phone or tablet?
Yes. The animation resizes to fit your screen and supports touch, so you can drag, tap and slide with your finger.
How should I study The Lymphatic System?
Read the summary and key ideas first, play with the interactive lab to see the idea in motion, then answer the quick check. If you get a question wrong, go back to the key idea it tests.
Do I need an account, and is my progress saved?
No account is needed. Marking a topic as learned is saved in your own browser, so it stays on that device and is not sent to a server.