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The Interstitial Fluid Compartment: Still Unrecognized or Biophysically Well Described?
Daniela Negrini1, Giuseppe Miserocchi2
1Department of Medicine and Technological Innovation (DIMIT), University of Insubria, Varese, Italy.
Comprehensive Physiology
|July 8, 2026
Summary
A proposed third circulatory system focuses on the interstitial compartment, a space identified 130 years ago. This review summarizes fluid dynamics, capillary filtration, and lymphatic drainage within this vital bodily system.
Area of Science:
- Physiology
- Circulatory System Biology
- Fluid Dynamics
Background:
- A novel "third bodily system for fluid circulation" has been proposed.
- This system corresponds to the interstitial compartment, conceptualized by Ernest Starling 130 years ago.
- Understanding this compartment is crucial for comprehending overall fluid balance.
Purpose of the Study:
- To review current physiological knowledge of the interstitial compartment.
- To analyze the morpho-functional features of this "third circulation".
- To provide an updated summary of key processes within the interstitial space.
Main Methods:
- Literature review of physiological knowledge.
- Analysis of data concerning capillary microfiltration.
- Examination of interstitial fluid dynamics and lymphatic drainage.
Main Results:
- The interstitial compartment functions as a distinct circulatory system.
- Capillary microfiltration dynamics are central to interstitial fluid formation.
- Lymphatic drainage plays a critical role in maintaining interstitial fluid homeostasis.
Conclusions:
- The interstitial compartment represents a significant, yet often overlooked, circulatory system.
- Further research into interstitial fluid dynamics and lymphatic function is warranted.
- This "third circulation" is essential for maintaining physiological balance.
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