Lymphatic System Overview

Functions of the Lymphatic System

• Transports lymph, a fluid similar to blood plasma.
• Lymph fluid is unidirectional in lymphatic vessels.
• Integral to immune defense by allowing lymphocytes to interact with antigens.

Formation of Lymph

• Blood capillaries leak fluid (interstitial fluid) into tissues.
• Interstitial fluid provides oxygen, nutrients, and removes waste.
• Lymph capillaries absorb interstitial fluid, now called lymph.
• Lymph moves through lymphatic vessels, aided by pressure and valves.

Structure & Function of Lymphatic System Components

Primary Lymphoid Organs

• Bone Marrow: Site of lymphocyte production.
• Thymus: Maturation site for T lymphocytes.

Secondary Lymphoid Organs and Tissues

• Lymph Nodes
  • Bean-shaped with immune cells (macrophages, dendritic cells, lymphocytes).
  • Structure: Cortex (B cells), Paracortex (T cells), Medulla.
  • Blood supply allows immune cells from blood to access lymph.
• Spleen
  • Located near the stomach.
  • Destroys old red blood cells and assists in immune response.
  • Structure: Red pulp (disposal of RBCs), White pulp (rich in lymphocytes).

Mucosa-Associated Lymphoid Tissues (MALT)

• Locations: Gastrointestinal, respiratory, urogenital tracts.
• Functions: Protects mucosal surfaces exposed to external environment.
• Specialized MALTs:
  • Gut-associated lymphoid tissues (GALT).
  • Bronchus-associated lymphoid tissues.
  • Nasal-associated lymphoid tissues.
  • Skin-associated lymphoid tissues.
• Contains lymphocytes and dendritic cells that sample antigens.

Key Processes

• Lymphatic vessels transport lymph from tissue to lymph nodes, then to the thoracic duct, and back into blood circulation.
• Adaptive immune responses are initiated in secondary lymphoid organs.
• Dendritic cells sample antigens and display them for immune response initiation.

Summary

• The lymphatic system is crucial for fluid balance and immune defense.
• Comprises primary (bone marrow, thymus) and secondary lymphoid organs (lymph nodes, spleen) and tissues (MALT).
• Ensures efficient interaction of lymphocytes with antigens and pathogens.