Abstract

The partition of fluid between the vascular and interstitial compartments is regulated by forces (hydrostatic and oncotic) operating across the microvascular walls and the surface areas of permeable structures comprising the endothelial barrier to fluid and solute exchange, as well as within the extracellular matrix and lymphatics. In addition to its role in the regulation of vascular volume, transcapillary fluid filtration also allows for continuous turnover of water bathing tissue cells, providing the medium for diffusional flux of oxygen and nutrients required for cellular metabolism and removal of metabolic byproducts. Transendothelial volume flow has also been shown to influence vascular smooth muscle tone in arterioles, hydraulic conductivity in capillaries, and neutrophil transmigration across postcapillary venules, while the flow of this filtrate through the interstitial spaces functions to modify the activities of parenchymal, resident tissue, and metastasizing tumor cells. Likewise, the flow of lymph, which is driven by capillary filtration, is important for the transport of immune and tumor cells, antigen delivery to lymph nodes, and for return of filtered fluid and extravasated proteins to the blood. Given this background, the aims of this treatise are to summarize our current understanding of the factors involved in the regulation of transcapillary fluid movement, how fluid movements across the endothelial barrier and through the interstitium and lymphatic vessels influence cell function and behavior, and the pathophysiology of edema formation.

Contents

• 1. Fluid Movement Across the Endothelial Barrier
  • 1.1 Hydrostatic and Oncotic Pressures, Surface Area, and Permeability Determine Exchange: The Starling Equation
  • 1.2 Relationships Between Transvascular Volume Flux and Hydrostatic Pressure: Determination of Hydraulic Conductivity and Effective Colloid Osmotic Pressure Gradient
  • 1.3 Assessment of Diffusive Permeability
  • 1.4 Convective Solute Transport Across the Microvascular Walls
  • 1.5 Capillary The Morphology Varies Among Organs in Accord with Function
  • 1.6 Transendothelial Filtration Modifies Arteriolar, Capillary and Venular Function
• 2. The Interstitium
  • 2.1 Composition, Structure and Three-Dimensional Organization of the Extracellular Matrix in the Interstitial Spaces
  • 2.2 Solute Exclusion and Osmotic Amplification in the Extracellular Matrix
  • 2.3 Compliance and Hydraulic Conductance in the Extracellular Matrix
  • 2.4 Fluid Flow in the Interstitium Modifies the Function of Tissue Cells
• 3. The Lymphatic Vasculature
  • 3.1 Anatomy and Nomenclature of the Lymphatic Vasculature
  • 3.2 Lymph Formation
  • 3.3 Interstitial Fluid Pressure and its Influence on Lymph Flow
  • 3.4 Lymphatic Solute Permeability
  • 3.5 Propulsion of Lymph by the Lymphatic Muscle Pump
  • 3.6 Lymphangiogenesis
  • 3.7 Tumors and Lymphatic Metastasis
  • 3.8 Cessation of Lymph Flow and its Immunological Consequences
• 4. Pathophysiology of Edema Formation
  • 4.1 The Margin of Safety Against Edema Formation – Edema Safety Factors
  • 4.2 Vasogenic Edema
  • 4.3 Hypoproteinemia
  • 4.4 Permeability Edema and Inflammation
  • 4.5 Neurogenic Inflammation
  • 4.6 Myxedema
  • 4.7 Lymphedema
• References