The property of blood capillary ENDOTHELIUM that allows for the selective exchange of substances between the blood and surrounding tissues and through membranous barriers such as the BLOOD-AIR BARRIER; BLOOD-AQUEOUS BARRIER; BLOOD-BRAIN BARRIER; BLOOD-NERVE BARRIER; BLOOD-RETINAL BARRIER; and BLOOD-TESTIS BARRIER. Small lipid-soluble molecules such as carbon dioxide and oxygen move freely by diffusion. Water and water-soluble molecules cannot pass through the endothelial walls and are dependent on microscopic pores. These pores show narrow areas (TIGHT JUNCTIONS) which may limit large molecule movement
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Blood-Air Barrier : Biology and regulation of blood-tissue barriers / edited by C. Yan Cheng
The barrier between capillary blood and alveolar air comprising the alveolar EPITHELIUM and capillary ENDOTHELIUM with their adherent BASEMENT MEMBRANE and EPITHELIAL CELL cytoplasm. PULMONARY GAS EXCHANGE occurs across this membrane
