Why is Lymph Called Filtered Blood?
Lymph is called filtered blood because it originates from blood plasma. As blood circulates through capillaries, some of the plasma leaks through tiny holes in the capillary walls. This escaped plasma, now called lymph, is essentially a filtered version of blood, lacking some of the components found in blood, such as red blood cells and most proteins. The lymphatic system then collects and transports this lymph, helping to maintain fluid balance and immune function.
The process isn't simply a passive filtration; it involves selective permeability. While larger components like red blood cells and large proteins remain in the bloodstream, smaller molecules and water pass into the surrounding tissues, forming the interstitial fluid. This interstitial fluid is then collected by lymphatic capillaries, becoming lymph.
- Blood Plasma: The starting point. It's the liquid part of blood, carrying nutrients, hormones, and waste products.
- Capillary Walls: These thin walls allow certain substances to pass through while retaining others.
- Interstitial Fluid: The fluid that surrounds cells and tissues.
- Lymphatic Capillaries: These tiny vessels collect the interstitial fluid, transforming it into lymph.
- Lymph: The clear, watery fluid that contains white blood cells, fats (chyle from the intestines), and proteins. It lacks the red blood cells and most of the larger proteins present in blood plasma.
Lymph's Role Beyond Filtration
While the term "filtered blood" emphasizes its origin, it's crucial to understand that lymph also has unique functions beyond simply being a filtered fluid. It plays a vital role in:
- Immune function: Lymph transports immune cells (lymphocytes) throughout the body, helping to fight infection.
- Fluid balance: The lymphatic system helps to remove excess fluid from tissues, preventing swelling (edema).
- Fat absorption: Lymph carries fats and other nutrients absorbed from the intestines.
The lymph nodes, part of the lymphatic system, further process the lymph, acting as filters that trap and remove foreign substances, pathogens, and cellular debris. They also contain lymphocytes that mount immune responses against these foreign invaders.
Several sources support this explanation:
- One source states: "As this lymph is formed from the blood which has come out through the capillaries it is called as filtered blood." [Source: brainly.in answer]
- Another source clarifies: "Lymph is called filtered blood because it is clear watery fluid without proteins and RBCs." [Source: embibe.com]
- A reputable medical source explains that the lymphatic system drains "extra fluid (called lymph) that has leaked from blood vessels into the tissues." [Source: cancer.ca]
