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Unformatted text preview: junctions. Sympathetic innervation of larger venules can alter venular tone which plays a role in regulating capillary hydrostatic pressure. Terminal Lymphatics Composed of endothelium with intercellular gaps surrounded by highly permeable basement membrane and are similar in size to venules terminal lymphatics end as blind sacs. Larger lymphatics also have smooth muscle cells. Spontaneous and stretch-activated vasomotion is present which serves to "pump" lymph. Sympathetic nerves can modulate vasomotion and cause contraction. One-way valves direct lymph away from the tissue and eventually back into the systemic circulation via the thoracic duct and subclavian veins (2-4 liters/day returned). 9 Pulmonary Circulation Mechanisms of Capillary Exchange
Fluid, electrolytes, gases, small and large molecular weight substances can transverse the capillary endothelium by several different mechanisms: diffusion, bulk flow, vesicular transport, and active transport. These mechanisms are depicted in the following figure and discussed in the subsequent text: Diffusion Particularly important for gases (O2 and CO2) and lipid-soluble substance...
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- Fall '07
- Hydrostatic Pressure