Lymphatic System Overview

Key Functions

• Fluid Return: Returns fluid from tissues back to the heart.
• Transport Large Molecules: Helps large molecules like hormones and lipids enter the blood.
• Immune Surveillance: Helps prevent infections from spreading.

Lymph Formation and Movement

• Blood flows through arteries under high pressure, reaching capillaries which are porous.
• 20 liters of fluid per day seep from capillaries into interstitial fluid; 17 liters reabsorbed, leaving 3 liters.
• Lymphatic Vessels: Collect excess interstitial fluid and return it to blood.
  • Lymph: Once fluid enters lymphatic vessels.

Lymphatic System Structure

• Not a Closed Loop: Fluid enters lymphatic capillaries and is eventually dumped into veins.
• Lymphatic Capillaries: Extremely permeable, allowing fluid entry when interstitial pressure is higher.
• Lymphatic Vessels: Contain valves to prevent backflow, move lymph through the system via muscle contractions.
• Lymphatic Trunks and Ducts: Collect lymph from body regions:
  • Right lymphatic duct: Right arm, head, and chest.
  • Thoracic duct: Rest of the body.

Special Roles

• Transport of Large Molecules: Hormones, fatty acids (in the form of chylomicrons) enter bloodstream via lymph.
• Immune Function: Lymphoid organs filter lymph, act as immune surveillance points.

Lymphoid Organs

• Diffuse Lymphoid Tissue: Found in gastrointestinal and respiratory tracts.
• Lymph Nodes: Filter lymph, present antigens to B and T cells.
• Spleen: Filters blood, destroys old blood cells, stores red blood cells and platelets.
• Thymus: Develops T-cells, active in early life.
• Tonsils: Trap pathogens from food and air.

Immune Process in Lymph Nodes

• Dendritic cells present antigens to B cells.
• B cells produce antibodies if foreign antigen detected.
• T cells circulate, searching for pathogens tagged by antibodies.

Recap

• Lymphatic System: One-way network transporting lymph to assist in nutrient transport and waste removal.
• Lymph Nodes: Key in cleansing lymph and immune defense.

Additional Information

• Educational Resources: Osmosis.org offers quizzes, flashcards, and more to learn about the lymphatic system.
• Content Contributors: Script by Andrea Day, edited by Risha Desai, voiced by Tanner Marshall, illustrations by Vince.
• Supporting Content Creation: Options to support through subscription, social media, or Patreon donations.