Lymphatic System

The lymphatic system supports immunity, fluid balance, fat absorption, and tissue repair. It filters pathogens and waste through lymph nodes, returns excess interstitial fluid to the bloodstream to prevent edema, absorbs dietary fats via lacteals in the small intestine, and delivers immune cells and nutrients to damaged tissues to support healing and inflammation resolution.

Immune Surveillance & Defense

• Lymphatic tissues are rich in white blood cells that identify and respond to infectious organisms
• Lymph nodes monitor lymph for pathogens, metabolic waste, and wandering cancer cells
• Immune cells within the nodes neutralize harmful substances before they enter circulation
• The system acts as a major early-warning network for the entire body

Fluid Balance & Movement

• Drains excess interstitial fluid from around cells and returns it to the bloodstream
• Prevents tissue swelling (edema) by maintaining proper fluid distribution
• Supports the venous system by returning plasma-like lymph to the bloodstream
• Helps keep blood volume stable and prevents fluid stagnation

Fat Absorption & Transport

• Specialized lymphatic capillaries called lacteals, located in the small intestine villi, absorb dietary fats
• Fats enter the lymphatic system before moving into the bloodstream
• This process ensures gradual, regulated lipid transport and prevents overload of the liver and blood vessels

Tissue Repair & Healing

• Delivers immune cells, nutrients, and hydration to damaged tissues
• Removes cellular debris and waste from injured areas
• Helps resolve inflammation by clearing out metabolic byproducts
• Plays a crucial role in restoring tissue integrity after injury

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The lymphatic system is a fluid-transport and immune network composed of vessels, lymph nodes, the spleen, thymus, tonsils, and gut-associated lymphoid tissues. It maintains fluid balance, filters waste, and supports immunity by circulating lymph—a clear fluid carrying immune cells, fats, and cellular debris. Lymph moves through one-way vessels without a central pump, relying on muscle contraction and breath to flow. Primary lymphatic organs (bone marrow and thymus) generate and mature immune cells, while nodes and tissues throughout the body monitor and respond to pathogens.

Lymphatic Vessels

• One-way vessels with valves that keep lymph moving in a single direction
• Interwoven with blood capillary beds; open-ended rather than closed-loop
• Movement depends on skeletal muscle activity, breathing, and smooth muscle tone
• No central pump (unlike the heart)
• Most lymph drains into the left subclavian vein

Encapsulated Lymphoid Tissues

Lymph Nodes

• Filter microorganisms, toxins, and waste
• House leukocytes (lymphocytes + monocytes)
• Monitor all incoming lymph
• Major clusters include:
  • Cervical (neck)
  • Axillary (armpit)
  • Inguinal (groin)
  • Popliteal (behind the knee)

Spleen

• Largest lymphatic organ
• Filters blood and lymph
• Stores blood and immune cells
• Assists in immune response and RBC recycling

Unencapsulated Lymphoid Tissues

Tonsils

• Provide early immune defense in upper respiratory and digestive tracts

GALT — Gut-Associated Lymphoid Tissue

• Lymphoid clusters throughout the GI mucosa
• Major center of immune surveillance and gut-immune interface

Primary Lymphatic Organs

Bone Marrow

• Site of blood cell formation
• B-cell maturation

Thymus Gland

• T-cell maturation
• Critical during early immune development

Lymph (the Fluid)

• Clear, slightly alkaline fluid circulating through lymph vessels
• Contains:
  • Water + electrolytes
  • Cellular waste
  • Dietary fats
  • Proteins
  • Larger particulates cleared from tissues