Which one of the following is a matching pair?
Lubb - sharp closure of AV valves at the beginning of ventricular systole
Dup - sudden opening of semilunar valves at the beginning of ventricular diastole
Pulsation of the radial artery - valves in the blood vessels
Initiation of the heart beat - Purkinje fibres
A.
Lubb - sharp closure of AV valves at the beginning of ventricular systole
The gradually increasing contraction of ventricular muscles during systole first causes the closure of bicupsid and tricupsid valves (AV valves), producing a low- pitched 'lubb' sound. Later, it causes the opening of the semilunar valves of systemic and pulmonary aorta. At the end of ventricular systole, semilunar valves shut, producing the second, louder heart sound, the 'dup'. Thus, each heart beat is accompained by a 'lubb- dup' sound.
