The endothelium functions as a semipermeable barrier between circulating vascular contents and the interstitium of the surrounding tissues, and maintenance of this barrier is essential for optimal organ function. For example, the lung is particularly sensitive to perturbations of barrier function because of the enormous surface area of the pulmonary vasculature. Disruption of the pulmonary endothelial lining leads to alveolar flooding during inflammatory conditions such as adult respiratory distress syndrome (ARDS) and sepsis and contributes significantly to the morbidity of these clinical syndromes. As a result, a comprehensive understanding of the regulatory mechanisms involved in endo-thelial permeability has important clinical implications. Current evidence supports an integral role for the endothe-lial cytoskeleton in dynamic modulation of vascular barrier function, with recent work highlighting the contribution of the microvasculature to this process. In this chapter, we will focus on the pulmonary vasculature as a model system to outline the cytoskeletal mechanisms that regulate endothe-lial permeability. Our discussion will begin with a general overview of regulatory mechanisms inherent to endothelial cells (ECs) throughout the vascular bed, and then we will proceed to highlight the permeability properties unique to the microvessel circulation.
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This ebook provides an introductory explanation of the workings of the human body, with an effort to draw connections between the body systems and explain their interdependencies. A framework for the book is homeostasis and how the body maintains balance within each system. This is intended as a first introduction to physiology for a college-level course.