1. In reference to the “lub-dup...lub-dup..”. sounds that are heard through a stethoscope when it is
placed over the heart, what causes the “lub” sound?
“Lub” is the closure of the AV causes the backflow of blood against them. The valves are elastic
and cause blood to surge into the ventricles creating vibrations.
2. In the auscultatory method of measuring the blood pressure, what causes the first Korotkoff
The first Korotkoff sound is the snapping sound first heard at the systolic pressure. Clear
tapping, repetitive sounds for at least two consecutive beats is considered the systolic pressure.
3. What are intercalated disks in the heart muscle? What are their functions?
Cardiac muscle consists of individual heart muscle cells connected by intercalated discs to work
as a single functional organ. Intercalated discs support synchronised contraction of cardiac
tissue. They occur at the Z line of the sarcomere.
4. How do the valves within the veins of the arms and legs help blood return to the heart?
Prevent the blood from being subject to gravity and falling towards the feet. The valves open
when the blood moves upwards (when the heart pumps the blood out of the ventricles (systo