Functional arrangement of rat diaphragmatic initial lymphatic network

Area of Science:

• Physiology
• Anatomy
• Lymphatic System

Background:

• Fluid and solute exchange between pleural and peritoneal cavities is poorly understood under physiological conditions.
• Potential role in ascites, pleural effusion, and tumor metastasis.

Purpose of the Study:

• To investigate pleuroperitoneal flux through the diaphragmatic lymphatic network.
• To assess the role of the transdiaphragmatic pressure gradient (Delta P(TD)) and lymphatic anatomy.

Main Methods:

• Measurement of transdiaphragmatic pressure gradient (Delta P(TD)) in anesthetized rats.
• Morphometrical analysis of diaphragmatic lymphatic network using light and electron microscopy.

Main Results:

• A pressure gradient exists from the abdominal to the pleural cavity (Delta P(TD) negative).
• Diaphragmatic lymphatics exhibit initial lymphatic vessel ultrastructure with unidirectional valves.
• Complex valve system identified in initial and collecting lymphatics.

Conclusions:

• Despite a favorable pressure gradient, physiological fluid bulk flow between pleural and peritoneal cavities via the diaphragmatic lymphatics is unlikely.
• The intricate lymphatic valve system appears to prevent significant fluid movement.