Lymphatic system

Two Overlapping Systems

  1. Lymphatic system → returns fluid to blood

  2. Lymphoid organs/tissues → houses immune cells

1.Lymphatic System — Fluid Recovery

  • ~20 L fluid filtered daily

  • ~17 L reabsorbed; 3 L become lymph

Lymphatic Vessels

Route:
Lymphatic capillaries → vessels → trunks → ducts

  • Right lymphatic duct: drains right upper body

  • Thoracic duct: drains rest of body

Flow maintained by:

  • Skeletal muscle pump

  • Respiratory pump

  • Valves

  • Smooth muscle contraction

Specialised Capillaries

  • Lacteals (small intestine): absorb dietary fats

2.Lymphoid Organs & Tissues

Primary Organs

  • Bone marrow – B cell maturation

  • Thymus – T cell maturation

Secondary Organs

  • Lymph nodes: filter lymph; activate lymphocytes

  • Spleen: filters blood; stores platelets; immune surveillance

  • Tonsils & MALT: protect mucosal surfaces

Lymph Nodes — Structure & Function

  • Afferent vessels → lymph enters

  • Passes through:

    • Subcapsular sinus

    • Cortex (B cells in follicles)

    • Paracortex (T cells)

    • Medulla

  • Efferent vessel → lymph exits

  • Sites of antigen presentation & activation

Clinical Connections

  • Lymphedema: lymph blockage (surgery, cancer)

Filariasis: parasitic worm → elephantiasis