Anatomy of Blood Vessels and the Interstitium

New Discovery: The Interstitium

• Discovery Year: 2018
• Structure: Described as a continuous fluid-filled space inside the body, filled with interstitial fluid (water and solutes).
• Function:
  • Acts as a shock absorber for the body.
  • Conduit for fluids entering the lymphatic system.
  • Potential route for cancer metastasis.
• Characteristics:
  • Described as a fluid-filled 3D latticework of connective tissue.
  • Found near lungs, skin, digestive tracts, and arteries.
  • Not visible post-mortem due to collapse; detected with modern imaging technology.
• Controversy: Not all researchers agree it's an organ.

Lymphatic System Overview

• Part of both cardiovascular and immune systems.
• Components:
  • Lymphatic vessels, organs, and tissues.
• Function:
  • Transports fluid and helps fight infections.
  • Returns excess interstitial fluid to venous circulation, preventing edema.

Interstitial Fluid and Lymph

• Process:
  • Blood plasma leaks out of capillaries becoming interstitial fluid.
  • Interstitial fluid enters lymph capillaries, turning into lymph.
  • Lymph is returned to bloodstream, becoming plasma again.
• Lymphatic Structures:
  • Vessels, lymph cells, lymph organs.
  • Lymph nodes filter bacteria and damaged cells.
• Color Coding in Diagrams:
  • Lymphatic vessels: Green (chartreuse).
  • Arteries: Red.
  • Veins: Blue.
  • Nerves: Yellow.

Lymphatic Vessels

• Lymphatic Capillaries:
  • Arise as blind-end vessels.
  • Interspersed among blood capillary beds.
  • Slightly larger than blood capillaries with closed ends.
  • One-way entry flaps allow interstitial fluid in but not out.
• Mechanism:
  • Muscle contractions move lymph through the system.
  • Overlapping endothelial cells act as one-way doors based on pressure difference.