Arteriovenous anastomosis

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An arteriovenous anastomosis is a short-circuit connection between an arteriole and a venole that can be opened and closed as part of the blood flow regulation. Arteriovenous anastomoses are important on the one hand for the sparing organ blood flow and on the other hand for the heat dissipation .

Organ blood flow

The generated from the heart blood flow not to all vessels while maintaining sufficient blood pressure to perfuse maximum. By opening arteriovenous anastomoses, capillary areas that supply cells with currently low metabolic activity can be bypassed. The control of the opening of these cross-connections is mainly done locally chemically via vascular substances.

Heat emission

There are arteriovenous anastomoses in the skin, which are used for thermoregulation. Due to their low vascular resistance , their opening is accompanied by a massive increase in blood flow, so that heat can be given off effectively. The blood flow to the arteriovenous anastomoses takes place in addition to the capillary blood flow, which is also pronounced when heat is required. The blood flow in both vascular systems is promoted by a low sympathetic muscle tone, whereby the arteriovenous anastomoses close with little constrictive activity.

In the fingers and toes there are glomus anastomoses , which are particularly suitable for heat dissipation due to their structure: The tangled, branched vessels lie in their own connective tissue capsule and are richly innervated.

The presence of arteriovenous anastomoses offers the advantage, compared to the likewise conceivable excessive blood flow in capillaries, that shifts in the local chemical environment (e.g. reduced CO 2 partial pressure) are avoided.

literature

  • Uwe Gille: Cardiovascular and immune system, Angiologia . In: Franz-Viktor Salomon et al. (Hrsg.): Anatomie für die Tiermedizin . Enke-Verlag, Stuttgart 2004, pp. 404-463. ISBN 3-8304-1007-7 .

Individual evidence

  1. ^ Schmidt, Lang, Heckmann: Physiologie des Menschen . 31st edition. Springer Medizin Verlag, Heidelberg 2010, ISBN 978-3-642-01650-9 , p. 588 .
  2. ↑ Renate Lüllmann-Rauch: Pocket textbook histology . 5th edition. Thieme, Stuttgart 2015, ISBN 978-3-13-129245-2 , p. 281 .
  3. ^ Schmidt, Lang, Heckmann: Physiologie des Menschen . 31st edition. Springer Medizin Verlag, Heidelberg 2010, ISBN 978-3-642-01650-9 , p. 623 .