What are teeth-shaped bundles of smooth muscle found only in the auricles?

Teeth-shaped bundles of smooth muscle found only in the auricles are known as pectinate muscles. These muscles are responsible for increasing the surface area of the atrial walls and aiding in the contraction of the atria during the cardiac cycle. They are primarily located in the right atrium and the anterior wall of the left atrium, contributing to the heart's efficient pumping mechanism.