BIOL 1010 Chapter Notes - Chapter 26: Extracellular Fluid, Epithelium, Exocytosis
14 May 2017
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Smooth endothelium walls but are reinforced by two other tissue layers. Outer layer connective tissue with elastic fibres enables the vessels to stretch and recoil. These layers are thicker and sturdier in arteries, providing strength and elasticity to accommodate the rapid flow and high pressure of blood pumped by the heart. Arteries are able to regulate blood flow by constricting or relaxing their smooth muscle layer. Thinner walled veins take blood back to the heart with low speed and pressure. Within large veins, flaps of tissue act as one-way valves, which allow blood to flow only toward the heart. Capillaries all the transfer of substances through their walls. The capillary wall consists of adjoining epithelial cells that enclose a lumen, or interior space. Lumen is large enough for red blood cells to tumble through in a single file. Interstitial fluid fills the space between the capillary and the muscle cells. Exchange of substances between blood and the interstitial fluid.
