Cardiovascular System Flashcards
What is the daily output of blood from the muscular pumps?
7000L/day each
What is the function of the aorta?
It is the main artery originating from the left ventricle that carries oxygenated blood away from the heart
What is the function of the left atrium?
Receives blood from the lungs and pumps into the ventricles
What is the function of the right atrium?
Receives blood from the venous circulation and pumps it into the ventricles
What is the function of the superior vena cava?
Returns deoxygenated blood from the systemic circulation to the right atrium of the heart
What is the function of the interior vena cava?
Carries deoxygenated blood from the lower and middle body into the right atrium
What is the function of the auricles?
They are a thin pouch if heart wall that helps the atrium to hold more blood by holding blood and contracting to pump
What is the peak pressure of the right ventricle?
27mmHg
What is the peak pressure of the left ventricle?
120mmHg
What is the peak pressure of the right atrium?
5mmHg
What is the peak pressure of the left atrium:
8mmHg
What are the 2 types of atrioventricular valves?
Bicuspid/mitral valve: left side
Tricuspid: right side
Describe the atrioventricular valves:
They are found between the atrium and the ventricles on the left (mitral) and right (tricuspid) sides of the heart. One edge is attatched to the wall of the heart and the other side is free so it is tethered by tendinous chords to prevent it from bursting upwards.
What is the purpose of chrodae tendine and papillary muscles?
To prevent the atrioventricular valves from going back up when the blood pushes against the valves after coming into the ventricles.
The 2 inlet valves (mitral and bicuspid) - atrioventricular are much larger than the outlet valves (aortic and pulmonary) - semilunar valves, why is this?
The inlets must be bigger because they are letting in the blood at a lower pressure so they need a larger diameter whereas in the outlet ones they are leaving at high pressure so they don’t need a large diameter.
What are the 2 types of outlet valves - semilunar valves?
Aortic valve
Pulmonary valve
Describe how ventricular outlet valves/ semilunar work?
When blood leaves during ventricular ejection, it leaves the ventricle and flows up into the artery. The pressure of the blood trying to reenter the ventricles forces the free edges of the cusps together
Do semilunar/ventricular outlet valves need papillary muscles and tendinous chords, why/why not?
No because they are smaller so they don’t need them
Where is the apex of the heart?
It is at the bottom and it points inferiorly, anteriorly and to the left.
What is the right border of the heart formed by?
The right atrium
What is the left border of the heart formed by?
The left ventricle
Describe the superior border of the heart:
It is the base border as it only attachment point of the heart and is tethered by blood vessels
Describe the pericardium:
It encloses the heart in a double walled bag. There is an inner layer (visceral pericardium) and outer layer (parietal pericardium) and they are both made by a single layer of squamous mesothelial cells. In the middle there is the pericardial space which is filled with serous fluid
What does the outer wall of the pericardium line?
The fibrous pericardium which is made up of collagen and is a tough fibrous sac.
Going from the blood to the outer pericardial sac, name all of the layers in between:
Blood, endocardium, myocardium (cardiac muscle), epicardium/visceral, pericardial space, parietal, fibrous, outer
What is cardiac temponade?
When the pericardial space has filled with blood
Describe how the valves of the heart are all connected to form the fibrous skeleton:
The fibres forming the tricuspid ring are incomplete and the pulmonary ring is absent. Both of these are associated with low pressure in the pulmonary pump. Fatty connective tissue is still present where the fibrous skeleton is incomplete.
Does the heart have nerves why/why not?
No it just has modified muscle that acts essentially as nerves.
Where is the AV node found?
Sitting in a hole in the fibrous skeleton
What is the function of the fibrous skeleton?
Conduction
Where is the SA node?
It is found at the junction between the superior vena cava and the right atrium
Where are the pacemaker cells that are influenced by hormones and peripheral nerves?
The SA node
What is the point of the 100m/s delay?
We don’t want the atrium and ventricles contracting at the same time
Describe the first stage of how an action potential is conducted down the heart:
The SA node can spontaneously depolarise and repolarise so the action potential travels out of the SA node and out to the atrial muscle. It is very slow 0.5m/s and results in atrial contraction. It ensures that the atrial contraction is even and coordinated.
Describe the second stage of how an action potential is conducted down the heart:
It begins at the AV node which can also spontaneously depolarise and repolarise on its own but much slower than the SA node. The speed o f contraction is very slow about 0.05m/s which results in a 100ms delay
Describe the third stage of how an action potential is conducted down the heart:
The action potential goes down the AV bundle and out to the purkinje fibres. The speed is very fast about 5m/s and results in even ventricular contraction (systole)
About how long is one cardiac cycle?
1s
List the order of one cardiac cycle:
Ventricular filling (diastole), atrial contraction, isovolumetric ventricular contraction (systole), ventricular ejection (systole), isovolumetric ventricular relaxation
Describe the stage of the cardiac cycle: ventricular filling
This is the stage of diastole where the phase commences as pressure in the ventricles drops below that of the atrium. The mitral valve opens quietly and blood begins to enter the ventricle.
When exercising, which phase shortens the most?
Ventricular filling
Describe the phase of the cardiac cycle: atrial contraction:
The left atrium contracts to complete filling of the ventricles. The rise in atrial pressure is small because firstly the muscle layer of the atrium is thin and secondly because there are no valves where the pulmonary veins enter the atrium so there is nothing to prevent backflow back into the veins.
Describe the phase of the cardiac cycle: isovolumetric ventricular contraction
This is the beginning of systole. This is where the 1st heart sound is heard as the ventricle begins to contract. Blood within the ventricle lifts backwards towards the atrium and the mitral valve closes (first heart sound). Ventricular pressure is still lower than aortic pressure so the aortic valve remains closed. For this brief moment of rising pressure both its inlet and outlet valves are closed.
Describe the phase of the cardiac cycle: Ventricular ejection
Systole continues but now ventricular pressure exceeds aortic pressure and the aortic valves open. Blood leaves the ventricle. Because blood is ejected into the aorta faster than it can run off into the distributing arteries, the pressure in the ventricle and the aorta continues to rise rapidly, however later in this phase the rate of ejection falls below the rate of run off and aortic and ventricular pressures level off and then begin to decrease.
Describe the phase of the cardiac cycle: Isovolumetric ventricular relaxation
The ventricle relaxes and as it does so ventricular pressure drops suddenly, flow reverses in the aorta and the aortic valve closes (second heart sound), as blood tries to re-enter the ventricle. The mitral valve is closed because ventricular pressure although falling, is still higher than atrial pressure.
At what stage of the cardiac cycle does the mitral valve open?
Ventricular filling (diastole)
At what stage of the cardiac cycle does the mitral valve close?
Isovolumetric ventricular contraction.
At what stage of the cardiac cycle does the aortic valve open?
Ventricular ejection
At what stage of the cardiac cycle does the aortic valve close?
Isovolumetric ventricular relaxation
Why is the first heart sound louder than the second?
Because the inlet valves are bigger than the outlet valves.
What does systolic pressure represent?
Maximum pressure inside the systemic artery.
What does diastolic pressure represent?
Lowest pressure inside systemic artery.
What are the six types of blood vessels in the order of how blood leaving the heart sees them?
Elastic artery, muscular artery, arterioles, capillary, venule, vein.