Capillaries

• Capillaries form capillary beds at exchange surfaces, which are many branched capillaries

  • These all have a narrow diameter to slow blood flow
• Capillaries adaptations: Narrow lumen

  • Slows blood flow
  • Red blood cells are squeezed flat against the side of a capillary, bringing them even closer to the cells to which they supply oxygen (reduces diffusion distance)
• Capillaries - Tiny vessels that link arterioles to venules
• Capillaries adaptations: Once cell thick (consisting of only a lining layer)

  • Short diffusion distance for exchanging materials between the blood and cells
  • Allows for rapid diffusion
• Capillaries adaptations: Fenestrations (gaps)

  • Between endothelial cells
  • Allow substances to diffuse out between
• Capillaries adaptations: Numerous and highly branched

  • Provides a large surface area for gas exchange
• Capillaries function:

  • To exchange metabolic materials such as o2, co2 and glucose between the blood and the cells of the body
• The flow of blood in capillaries is much slower. This allows more time for the exchange of materials
• Capillary adaptations: Spaces between the lining (endothelial) cells called fenestrations

  • Allow white blood cells to escape in order to deal with infections within tissues
• Capillaries have a narrow diameter

  • No cell is far from a capillary and there is a short diffusion pathway