The dotted lines indicate part of the left coronary artery which is
concealed by the left auricle.
]
The =left coronary artery= (A. coronaria sinistra) arises from the left
posterior sinus of the aorta, passes to the left behind the origin of
the pulmonary artery, and divides into two branches. The =descending
branch= (Ramus descendens) passes down the left ventricular groove
toward the apex. The =circumflex branch= (Ramus circumflexus) runs
backward in the coronary groove, in which it winds around to the right
side.