Flow of Blood in the Capillaries Vasomotion

Blood usually does not flow continuously through the capillaries. Instead, it flows intermittently, turning on and off every few seconds or minutes. The cause of this intermittency is the phenomenon called vasomotion, which means intermittent contraction of the metarte-rioles and precapillary sphincters (and sometimes even the very small arterioles as well).

Regulation of Vasomotion. The most important factor found thus far to affect the degree of opening and closing of the metarterioles and precapillary sphincters is the concentration of oxygen in the tissues. When

Endothelial cell

Endothelial cell

cleft

Figure 16-2

cleft

Figure 16-2

Structure of the capillary wall. Note especially the intercellular cleft at the junction between adjacent endothelial cells; it is believed that most water-soluble substances diffuse through the capillary membrane along the clefts.

the rate of oxygen usage by the tissue is great so that tissue oxygen concentration decreases below normal, the intermittent periods of capillary blood flow occur more often, and the duration of each period of flow lasts longer, thereby allowing the capillary blood to carry increased quantities of oxygen (as well as other nutrients) to the tissues. This effect, along with multiple other factors that control local tissue blood flow, is discussed in Chapter 17.

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Responses

  • Dieter
    Where is vasomotion found?
    1 year ago
  • alexander
    How frequent is vasomotion in capillareies?
    6 months ago
  • louise
    How do precapillary sphincters help with vasomotion?
    2 months ago
  • feorie
    What is the affect of vasomotion on blood pressure?
    2 months ago
  • barry reilly
    How does vasomotion work?
    18 days ago

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