The Lymphatic System – Simple Explanation

Your body stays healthy by fighting off germs (called pathogens), getting rid of harmful toxins, healing damaged tissues (like cuts, burns, or sun damage), and removing harmful or cancerous cells. The ability to fight disease is called resistance. If your body can’t fight off illness easily, that’s called susceptibility.

There are two types of resistance:

1. Nonspecific resistance – General defences that protect against many different germs, like your skin, stomach acid, fever, or inflammation.
2. Immunity – A targeted defence system where certain white blood cells (lymphocytes) fight specific germs or foreign substances.

The system responsible for this targeted defence is called the lymphatic system.

What is the Lymphatic System?

The lymphatic system includes:

• A clear fluid called lymph
• Lymphatic vessels that carry the lymph
• Lymphatic tissues and organs (like lymph nodes and the spleen)
• Bone marrow, where immune cells (lymphocytes) are made

Lymph and interstitial fluid (the fluid between cells) are basically the same – it’s called lymph once it enters the lymphatic vessels.

Functions of the Lymphatic System

1. Drains extra fluid from tissues and returns it to the blood.
2. Carries fats and fat-soluble vitamins (A, D, E, K) from your gut to your blood.
3. Protects you from infection and disease through immune responses:
   
   • T cells kill infected or damaged cells.
   • B cells produce antibodies to attack specific invaders like viruses or bacteria.

How Lymph Travels

• Lymph starts in tiny vessels called lymphatic capillaries, found between your body’s cells.
• These capillaries join to form larger lymphatic vessels, which carry lymph through lymph nodes where harmful substances are filtered out.
• These vessels are like veins but have thinner walls and more valves to keep fluid moving in one direction.

In your skin, these vessels run near veins. Inside your organs, they often follow arteries.

Lymphatic Capillaries

• Found all over the body, except in:
  
  1. Areas without blood (like cartilage)
  2. The brain and spinal cord
  3. The spleen’s core
  4. Bone marrow
• They are slightly bigger than blood capillaries.
• Their structure allows fluid to enter easily, but not leak back out, helping keep body tissues balanced.