sinoatrial

sinoatrial /si·no·atri·al/ (si?no-a´tre-al) pertaining to the sinus venosus and the atrium of the heart.

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si·no·a·tri·al (sn-tr-l) or si·nu·a·tri·al (sn-tr-l, sny-)

adj. Abbr. S-A

Relating to the venous sinus and the right atrium of the heart.

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sinoatrial (SA) node (sī´nōā´trēl),

n a cluster of hundreds of cells located in the right atrial wall of the heart near the opening of the superior vena cava. It constitutes a knot of modified heart muscle that generates impulses, which travel swiftly throughout the muscle fibers of both atria, causing them to contract.

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sinoatrial

pertaining to the sinus venosus and the atrium of the heart or to the sinoatrial node; abbreviated S-A, SA.

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sinoatrial block

an absence of a discharge from the sinoatrial node. The heart is regular unless there is an underlying atrial arrhythmia. Considered to be within the limits of normality provided it disappears with exercise.

sinoatrial node

a collection of atypical muscle fibers and nerve endings in the wall of the right atrium, adjacent to the sulcus terminalis, where the rhythm of cardiac contraction is usually established; therefore also referred to as the pacemaker of the heart. Called also sinoatrial bundle, Keith's node, Keith-Flack node.