Leo pressed his own palm to his ribs. “Mine sound okay?”
Dr. Elara Vance had listened to thousands of heartbeats. But today, with the stethoscope pressed to a young boy’s chest, she paused. what causes the lub dub sound of the heartbeat
“Exactly. That’s your blood saying, ‘No going back!’” She tapped the paper. “Then the heart keeps pushing. Blood shoots into the big pipes—the aorta and pulmonary artery. The second sound, the dub , happens when the heart relaxes. Those two exit doors—the aortic and pulmonic valves—slam shut. Dub. ” Leo pressed his own palm to his ribs
Leo mimed a slam. “ Lub. ”