In otherwise healthy people, local tissue death follows obstruction of

 A. False  Flow through the circle of Willis normally maintains the viability of the tissue.

B. True  There is no significant collateral circulation.

C. False  Normally there is adequate collateral circulation. However, if there is advanced arterial disease, sudden obstruction may cause gangrene.

D. True  The collateral circulation is not good enough to prevent this.

E. False  The liver has a dual blood supply; the hepatic artery flow can maintain viability.