| What is the difference between arterial and venous systems? | Arterial vessels contain oxygenated blood, and venous vessels carry blood that is low in oxygen. Arteries specifically carry blood “away” from the heart, veins carry blood “toward” the heart. |
| Describe the capillary structure | Diameter 5-10 μm. Single endothelial layer, surrounded by the basement membrane. Capillaries permit the passage of water, metabolic products, O2, CO2and more. Capillary flow dictated by demand (not continuous). |
| Explain capillary blood flow | Intermittent flow, known as vasomotion caused by intermittent contraction of metarterioles and precapillary sphincters. Flow through the capillary bed is determined by the average of all flow through capillaries supplying that bed. Controlled in proportion to metabolic demand and the release of vasoactive substances in tissue bed. |
| Describe diffusion through capillary membrane in regards to governing capillary exchange and fluid movement | Exchange of water, gases, nutrients and other substances predominantly via diffusion Lipid-soluble substances (i.e. O2, CO2) can diffuse directly through cell membrane of capillary. Water-soluble (non lipid-soluble) substances (i.e. water, glucose, sodium) diffuse through intracellular clefts located between endothelial cells. |
| Describe fluid filtration across capillaries in regards to governing capillary exchange and fluid movement | Fluid filteration across capillaries are determined by starling forces Capillary Hydrostatic Pressure and Interstitial Fluid Pressure Plasma Colloid Osmotic Pressure and InterstitialColloid Osmotic Pressure However fluid filteration acorss capillaries also: Elevated capillary pressure at arterial end results in a net outward force. Lower capillary pressure at venous end, leads to a net inward force. |
