How does the fluid in blood become lymph?

As blood travels through capillaries, some of the fluid portion (also known as plasma) is pushed out of the capillaries and into the interstitial spaces (the spaces between cells). This fluid is called interstitial fluid.

Interstitial fluid is very similar in composition to blood plasma, except that it contains fewer proteins. Some of the interstitial fluid is then collected by lymphatic vessels, which are small vessels that run throughout the body. The lymphatic vessels carry the interstitial fluid back to the bloodstream.

As the interstitial fluid travels through the lymphatic vessels, it is filtered and purified. This process removes waste products and debris from the fluid. The filtered fluid is then called lymph.

Lymph is a clear, colorless fluid that is made up of water, proteins, fats, and white blood cells. It helps to protect the body from infection and disease.