Lymphatic System and Its Functions

Introduction

• Analogy of airport security line to blood flow in circulatory system
• Focus on lymphatic system's role in supporting cardiovascular and immune systems

Lymphatic System Overview

• Main Roles:
  • Maintains homeostasis by returning most diverted fluids to blood
  • Prevents swelling and fluid build-up in the body
  • Supports immune system by filtering pathogens

Structure of the Lymphatic System

• Three Main Parts:
  • Lymph: Watery fluid, originating as blood plasma
  • Lymphatic Vessels: Network reabsorbing fluids
  • Lymph Nodes: Checkpoints for monitoring and cleansing lymph
• Lymphoid Organs:
  • Spleen, Thymus, Adenoids, Tonsils
  • Special defensive cells to fight infection

Fluid Movement and Collection

• Originates in capillary beds of the circulatory system
• Daily fluid exchange:
  • 20 liters forced out
  • 17 liters reabsorbed by capillaries
  • 3 liters become lymph

Lymphatic Capillaries

• Loosely overlapping endothelial cells form flap-like valves
• Valves open to relieve pressure and take in fluid

Lymphatic Vessels and Ducts

• Operate under low pressure, similar to veins
• Two Major Ducts:
  • Right lymphatic duct: Drains upper right torso, arm, head, and thorax
  • Thoracic duct: Drains rest of body

Importance of Lymphatic System

• Blood Fluid Recovery:
  • Recovers 3 liters of blood fluid per day
  • Ensures stable blood pressure and oxygen delivery
• Immune Function:
  • Lymph nodes inspect lymph for pathogens
  • Lymphocytes trigger immune responses when necessary

Lymphoid Organs and Tissues

• Mucosa-associated lymphoid tissues (MALTs):
  • Found in mucous membranes (e.g., respiratory, digestive tracts)
  • Tonsils and Peyer’s patches act as checkpoints
• Appendix:
  • Contains lymphoid tissue, not useless

Conclusion

• Lymphatic system supports cardiovascular and immune systems
• Filters and returns interstitial fluid to bloodstream
• Houses lymphocytes for pathogen defense

Acknowledgments

• Thank you to Linnea Boyev, Patreon patrons, and Crash Course team members involved in creating the lecture.