MEDICAL PHYSIOLOGY

Detailed explanation-1: -However, when the ventricles relax, arterial pressure exceeds ventricular pressure and the semilunar valves snap shut. This is due to the elevated pressures in the aorta and the pulmonary artery pushing the blood back toward the ventricles to close the semilunar valves.

Detailed explanation-2: -The semilunar valves open when the ventricular muscle contracts and generates blood pressure within the ventricle higher than within the arterial tree. When the heart muscle relaxes the diastole phase begins again.

Detailed explanation-3: -When the left ventricle contracts, the mitral valve closes and the aortic valve opens. This is so blood flows into the aorta and out to the rest of the body. While the left ventricle is relaxing, the right ventricle also relaxes. This causes the pulmonary valve to close and the tricuspid valve to open.

Detailed explanation-4: -Isovolumetric relaxation (d-e): When the ventricular pressures drop below the diastolic aortic and pulmonary pressures (80 mmHg and 10 mmHg respectively), the aortic and pulmonary valves close producing the second heart sound (point d).

Detailed explanation-5: -3.4. During the isovolumic relaxation, the second heart sound appears (fig. 3.4). This sound is caused by vibrations of the semilunar valves, the adjacent myocardium and blood due to the closure of the semilunar valves.