The Functions Of The Heart Valves Flashcards
What are the A-V valves ?
The tricuspid and mitral valves
What is the function of AV valves?
Prevent backflow of blood from the ventricles into the atria during systole.
What are the semilunar valves?
The aortic and pulmonary valves
What is the function of semilunar valves?
Prevent backflow of blood into the ventricles from the aorta and pulmonary arteries into the ventricles during the diastole
What is the function of papillary muscles?
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.
What happens if a chordae tendineae rupture or papillary muscle paralyze?
It will cause bulging of the AV valves into the atria and induce backflow of blood from the ventricles into the atria.
What is the cause of semilunar valve closure?
The high end systolic pressure in the aorta and pulmonary arteries causes the semilunar valves to snap close.
Under normal physiological conditions what cause the systolic pressure in the arteries to reach 120mmHg?
The stretching of the elastic arterial walls due to the sudden increase in the volume of blood in it.
What causes the incisura in the aortic pressure curve?
It is the transient backflow of blood shortly before the closure of the aortic valve
What is the physiology of diastolic pressure?
It is the pressure within the aorta before the ventricle contracts for the next diastole.
What proportion of systolic pressure is the diastolic pressure?
2/3
What is the first heart sound?
It is the low pitch long lasting vibration caused by the closure of the AV valves.
What is the second heart sound?
It is the brief duration rapid snap sound caused by the closure of the semilunar valves.
What is stroke work output of the heart?
It is the amount of energy that the heart converts to work during each heart beat to pump blood into the arteries.
What is volume pressure work or external work of the heart?
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.
What is kinetic energy of blood flow?
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.
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?
Aortic stenosis
The kinetic energy of blood flow is proportional to what?
The mass of the blood ejected X the velocity of the ejection ^2
What is the non- contracting ventricular volume before the diastolic pressure raises ?
150 ml ( this blood passively diffuses to the ventricles).
What are the causes of ventricular diastolic pressure increase after the non- contracting ventricular volume reaches the threshold volume (150ml)
1) fibrous tissue in the heart that will stretch no more.
2) the pericardium of the heart gets filled nearly to its limit
What is the maximum systolic pressure of the left ventricle?
250 to 300 mmHg
What is the maximum systolic pressure of the right ventricle?
60 to 80 mmHg
Explain left ventricular volume- pressure diagram of cardiac cycle work output?
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.
What is the definition of preload in muscle contraction?
It is the degree of tension on the muscle during contraction.
What is the definition of after load in muscle contraction?
It is the load against which the muscle exert it’s contractile force.
What is the preload in cardiac muscle?
It is the end diastolic pressure when the ventricles have become filled.
What is the after load in cardiac muscle contraction?
It is the pressure in the aorta and the resistance of the circulation just before the systolic ejection.
