The Lymphatic System: Components & Immune Functions

The lymphatic system is a parallel circulatory network essential for fluid balance, fat absorption, and immune defense. Its main components:

1. Lymph

Clear fluid derived from interstitial fluid, rich in lymphocytes (especially T and B cells). Transports immune cells and waste.

2. Lymphatic Vessels

Thin-walled, valved capillaries and collecting vessels that drain lymph from tissues toward nodes. Rely on muscle contraction and breathing for flow.

3. Lymph Nodes

Bean-shaped filters strategically clustered (neck, axilla, groin, abdomen). Trap pathogens, cancer cells, and debris; activate adaptive immune responses.

4. Spleen

Largest lymphoid organ. Filters blood, removes old/damaged RBCs, stores platelets, and mounts immune responses to blood-borne antigens.

5. Thymus

Primary lymphoid organ where T cells mature and undergo selection. Most active in childhood; involutes with age.

6. Bone Marrow

Site of hematopoiesis—produces all blood cells, including B cells (which mature here) and lymphocyte precursors.

Additional Lymphoid Tissue

Tonsils, Peyer's patches (intestines), appendix, and mucosa-associated lymphoid tissue (MALT) guard mucosal entry points.