Capillary Fluid Exchange: Regulation, Functions, and Pathology

Description

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. Table of Contents: Fluid Movement Across the Endothelial Barrier / The Interstitium / The Lymphatic Vasculature / Pathophysiology of Edema Formation Fluid Movement Across the Endothelial Barrier......Page 9 The Starling Equation......Page 10 Hydraulic Conductivity......Page 14 Assessment of Diffusive Permeability......Page 17 Convective Solute Transport Across the Microvascular Walls......Page 19 Capillary The Morphology Varies Among Organs......Page 23 Transendothelial Filtration Modifies Vascular Function......Page 26 Composition, Structure and Three-Dimensional Organization of the Extracellular Matrix in the Interstitial Spaces......Page 29 Solute Exclusion and Osmotic Amplification......Page 31 Compliance and Hydraulic Conductance in the Extracellular Matrix......Page 33 Fluid Flow in the Interstitium Modifies the Function of Tissue Cells......Page 34 Anatomy and Nomenclature of the Lymphatic Vasculature......Page 41 Lymph Formation......Page 43 Lymphatic Solute Permeability......Page 44 Propulsion of Lymph by the Lymphatic Muscle Pump......Page 48 Lymphangiogenesis......Page 50 Tumors and Lymphatic Metastasis......Page 52 Cessation of Lymph Flow and its Immunological Consequences......Page 53 Pathophysiology of Edema Formation......Page 55 The Margin of Safety Against Edema Formation -- Edema Safety Factors......Page 56 Vasogenic Edema......Page 62 Permeability Edema and Inflammation......Page 66 Myxedema......Page 67 Lymphedema......Page 68 References......Page 71