The Functions Of The Heart Valves

Question 1

What are the A-V valves ?

Answer 1

The tricuspid and mitral valves

Question 2

What is the function of AV valves?

Answer 2

Prevent backflow of blood from the ventricles into the atria during systole.

Question 3

What are the semilunar valves?

Answer 3

The aortic and pulmonary valves

Question 4

What is the function of semilunar valves?

Answer 4

Prevent backflow of blood into the ventricles from the aorta and pulmonary arteries into the ventricles during the diastole

Question 5

What is the function of papillary muscles?

Answer 5

The papillary muscles are attached to the vanes of the AV valves by chordae tendineae. They contract during ventricular contraction and pull the vanes of the AV valves inward to prevent their bulging into the atria.

Question 6

What happens if a chordae tendineae rupture or papillary muscle paralyze?

Answer 6

It will cause bulging of the AV valves into the atria and induce backflow of blood from the ventricles into the atria.

Question 7

What is the cause of semilunar valve closure?

Answer 7

The high end systolic pressure in the aorta and pulmonary arteries causes the semilunar valves to snap close.

Question 8

Under normal physiological conditions what cause the systolic pressure in the arteries to reach 120mmHg?

Answer 8

The stretching of the elastic arterial walls due to the sudden increase in the volume of blood in it.

Question 9

What causes the incisura in the aortic pressure curve?

Answer 9

It is the transient backflow of blood shortly before the closure of the aortic valve

Question 10

What is the physiology of diastolic pressure?

Answer 10

It is the pressure within the aorta before the ventricle contracts for the next diastole.

Question 11

What proportion of systolic pressure is the diastolic pressure?

Answer 11

2/3

Question 12

What is the first heart sound?

Answer 12

It is the low pitch long lasting vibration caused by the closure of the AV valves.

Question 13

What is the second heart sound?

Answer 13

It is the brief duration rapid snap sound caused by the closure of the semilunar valves.

Question 14

What is stroke work output of the heart?

Answer 14

It is the amount of energy that the heart converts to work during each heart beat to pump blood into the arteries.

Question 15

What is volume pressure work or external work of the heart?

Answer 15

It is the proportion of stroke work output that the ventricles use to pump blood from the low pressure veins to the high pressure arteries.

Question 16

What is kinetic energy of blood flow?

Answer 16

It is the proportion of the stroke work output that the ventricles use to accelerate the blood to its ejection velocity through the pulmonary arteries and aorta.

Question 17

Kinetic energy of blood flow is trivial under physiological states. However, more than 50% of the stroke work out put needs to be used to accelerate the systolic ejection velocity in what condition?

Answer 17

Aortic stenosis

Question 18

The kinetic energy of blood flow is proportional to what?

Answer 18

The mass of the blood ejected X the velocity of the ejection ^2

Question 19

What is the non- contracting ventricular volume before the diastolic pressure raises ?

Answer 19

150 ml ( this blood passively diffuses to the ventricles).

Question 20

What are the causes of ventricular diastolic pressure increase after the non- contracting ventricular volume reaches the threshold volume (150ml)

Answer 20

1) fibrous tissue in the heart that will stretch no more.
2) the pericardium of the heart gets filled nearly to its limit

Question 21

What is the maximum systolic pressure of the left ventricle?

Answer 21

250 to 300 mmHg

Question 22

What is the maximum systolic pressure of the right ventricle?

Answer 22

60 to 80 mmHg

Question 23

Explain left ventricular volume- pressure diagram of cardiac cycle work output?

Answer 23

Phase 1: period of filling
It begins with the end systolic volume of 50 ml and end systolic ventricular pressure of 2 to 3 mmHg. Diastolic filling increases the ventricular volume to 120 mL and the diastolic ventricular pressure to 5 to 7mmHg, leading to the closure of the mitral valve.
Phase 02: period of isovolumic contraction
At this phase the ventricular volume doesn’t change but the pressure raises to 80 mmHg to equalize the pressure within the aorta.
Phase 3: Period of ejection
During ejection the systolic pressure raises even higher due to more stronger contraction of the ventricle. While the ventricular volume decreases due to the opening of the aortic valves.
Phase 04: period of isovolumic relaxation
At this phase the aortic valve closes and the ventricular pressure returns to baseline diastolic pressure 2-3 mmHg and the ventricular volume to end systolic volume ie. 50 mL.

Question 24

What is the definition of preload in muscle contraction?

Answer 24

It is the degree of tension on the muscle during contraction.

Question 25

What is the definition of after load in muscle contraction?

Answer 25

It is the load against which the muscle exert it’s contractile force.

Question 26

What is the preload in cardiac muscle?

Answer 26

It is the end diastolic pressure when the ventricles have become filled.

Question 27

What is the after load in cardiac muscle contraction?

Answer 27

It is the pressure in the aorta and the resistance of the circulation just before the systolic ejection.