Heart Anatomy and Cardiac Cycle - Anatomy and Physiology
- Why is the wall of the left ventricle much thicker than that of the right ventricle?
- The left ventricle pumps blood into the systemic circuit, against much higher pressure and resistance than the pulmonary circuit.
- When does the mitral valve open during the cardiac cycle?
- When left ventricular pressure falls below left atrial pressure at the end of isovolumetric relaxation, which begins ventricular filling.
- When does the aortic valve open during the cardiac cycle?
- When left ventricular pressure rises above aortic pressure, which begins the ejection phase.
- Where do the coronary arteries arise?
- From the base of the ascending aorta, just above the aortic valve.
- Which valve lies between the right atrium and the right ventricle?
- The tricuspid valve.
- At rest, how does most ventricular filling occur?
- Passively during ventricular diastole, before the atria contract; atrial systole adds only the final portion (roughly 20 to 30 percent).
- The fossa ovalis in the interatrial septum is a remnant of which fetal structure?
- The foramen ovale, which let blood pass from the right atrium to the left atrium in the fetus.
- Which valve lies between the left atrium and the left ventricle?
- The mitral (bicuspid) valve.
- What event produces the first heart sound (S1)?
- Closure of the atrioventricular (tricuspid and mitral) valves at the start of ventricular systole.
- What event produces the second heart sound (S2)?
- Closure of the semilunar (aortic and pulmonary) valves at the start of ventricular diastole.
- What is the state of the heart valves during isovolumetric contraction?
- All four valves are closed, so ventricular pressure rises while ventricular volume stays constant.
- Which structures prevent the atrioventricular valve cusps from everting into the atria during ventricular contraction?
- The chordae tendineae, anchored to papillary muscles that tense as the ventricle contracts.