If the cusps of an atrioventricular valve are damaged or functionally impaired so that they do not close completely during the normal point in the cardiac cycle, blood may flow backwards. this is called
b) regurgitation
c) thrombosis
d) automaticity
e) nodal depolarization

B) Regurgitation

Explanation:

Regurgitation refers to the backward flow of blood due to any reasons. Presence of atrioventricular valves between atrium and ventricle prevents the regurgitation, that is backward flow of blood. Structural or functional damage of any atrioventricular valves does not allow them to prevent the regurgitation.  

Example: Valvular insufficiency is the condition wherein the cusps of the valves (mostly the mitral valve) become stiff and leads to backward flow of blood.

answer: blah

explanation:

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answer : haversian

[explanation: -(compact bone is organized as parallel columns, known as haversian systems, which run lengthwise down the axis of long bones. these columns are composed of lamellae, concentric rings of bone, surrounding a central channel, or haversian canal, that contains the nerves, blood vessels, and lymphatic system of the bone)]