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How does the endothelium help regulate movement between blood and body tissues?
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Circulatory system
Human circulatory system.
The endothelium acts as a semipermeable barrier that regulates the exchange of substances between the bloodstream and surrounding tissues through three primary modes of transport:12
- Diffusion: Substances that are soluble in the lipid membrane of endothelial cells, such as oxygen and carbon dioxide, can pass directly through the cell membranes.1
- Ultrafiltration: Water-soluble substances that are insoluble in the lipid membrane, such as glucose or certain wastes, pass through minute, water-filled pores in the endothelial membranes.1
- Receptor-mediated transport: Specific substances, such as cholesterol, are transported across the endothelium by specialized receptors.1
Beyond these transport mechanisms, the endothelium plays a broader role in maintaining vascular health by regulating blood clotting, inflammation, and the diameter of blood vessels. By controlling the movement of nutrients, gases, hormones, and immune cells, the endothelium ensures that tissues receive necessary supplies while effectively removing metabolic waste products.2