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Arteriovenous anastomosis
Latin	anastomosis arteriovenosa

A arteriovenous anastomosis is a connection between two blood vessels, resulting in multitude of arteries and veins serving the same volume of tissue. Anastomoses occur normally in the body in the circulatory system, serving as backup routes for blood to flow if one link is blocked or otherwise compromised, but may also occur pathologically.

Contents 1 Physiologic 1.1 Coronary 2 Pathological 3 References

[edit] Physiologic

Arterial anastomoses includes actual arterial anastomoses (eg. palmar arch, plantar arch) and potential arterial anastomosis(eg. coronary arteries and cortical branch of cerebral arteries). An example of surgical anastomosis occurs when a segment of intestine is resected and the two remaining ends are sewn or stapled together (anastomosed), for example Roux-en-Y anastomosis. The procedure is referred to as intestinal anastomosis.

There are many examples of normal anastomoses in the body. However clinically important examples include:

• Circle of Willis (in the brain)
• scapular anastomosis (for the subclavian vessels)
• joint anastomoses - clinically very important. Almost all joints receive anastomotic blood supply from more than one source. Examples include knee (and geniculate arteries), shoulder (and circumflex humeral), hip (and circumflex iliac) and ankle. See also patellar network.
• pelvic anastomoses
• abdominal anastomoses
• hand and foot anastomoses (which include the palmar and plantar arches)
• Coronary: anterior and posterior interventricular arteries of the heart

[edit] Coronary

Coronary anastomoses are a clinically vital subject: the coronary anastomosis is the blood supply to the heart. The coronary arteries are vulnerable to arteriosclerosis and other effects. Inadequate supply to the heart will lead to chest pains (angina) or a heart attack (myocardial infarction).

Coronary anastomoses are anatomically present though functionally obsolete. There was some suggestion that they may be helpful if a problem develops slowly over time (this will need to be verified) but in the case of the pathogenesis of CHD they do not provide a sufficient blood flow to prevent infarction.

There are anastomoses between the Circumflex and right coronary arteries and between the anterior and posterior inter-ventricular arteries. In the normal heart these anastomoses are non-functional.

[edit] Pathological

Pathological anastomoses result from trauma or disease and may involve veins, arteries, or intestines. These are usually referred to as fistulas. In the cases of veins or arteries, traumatic fistulas usually occur between artery and vein. Traumatic intestinal fistulas usually occur between two loops of intestine (enetero-enteric fistula) or intestine and skin (enterocutaneous fistula). Portacaval anastomosis, by contrast, is an anastomosis between a vein of the portal circulation and a vein of the systemic circulation, which allows blood to bypass the liver in patients with portal hypertension, often resulting in hemorrhoids, esophageal varices, or caput medusae.

Circulatory anastomoses between monochorionic twins may result in twin-to-twin transfusion syndrome.^[1]

[edit] References

v • d • e Circulatory system: Arteries and veins (TA A12.2-3, GA 6.543/GA 7.641) Systemic circulation (Heart ) → Aorta → Arteries → Arterioles → Capillaries → Venules → Veins → Vena cava → (Heart) Pulmonary circulation (Heart) → Pulmonary arteries → (Lungs) → Pulmonary vein → (Heart) Blood vessels Endothelium · Tunica intima · Tunica media · Tunica externa Vasa vasorum · Vasa nervorum Rete mirabile · Arteriovenous anastomosis Arteries Nutrient artery Veins Vena comitans · Superficial vein · Deep vein · Emissary veins · Venous plexus vascular navs: anat/physio/dev, noncongen/systemic vasculitis/congen/neoplasia, symptoms+signs/eponymous, proc