Cardiac Flashcards
What is the difference between an artery and vein
Arteries take blood away from the heart- therefore they are exiting the ventricles, and Veins are carrying blood back to the heart.
Describe the path of the pulmonary circuit vs the systemic circuit
The pulmonary circuit from RV to the lung to the LV. The systemic circuit is from the LV to the systems (limbs, kidneys, brain, liver and gut) and then back to the RV.
Describe the purpose of pulmonary circuit vs the systemic circuit (what type of blood)
Pulmonary takes deoxygenated blood through P arteries to the Lungs for gas exchange and then oxygenated blood to LV. Systemic arteries deliver oxygenated blood to systems where there is gas exchange and deoxygenated blood carried by systemic veins back to the RV. For both circuits gas exchange is at a capillary bed at the organ.
Compare the blood volume and pressure of the two systems
P has medium pressure and medium resistance compared to S which has lots of vessels so high resistance and therefore high pressure.
S also has 84% of blood volume, (veins are reservoir). P has 9% of blood volume. 7% is in the Ventricles/atrium.
What is the total blood volume and output on an average person
Blood volume is 5L. Output is 5L/minute at rest
Describe the unusual venous draining of the gut
The deoxygenated blood from the gut also carries a lot of nutrients so it is delivered to the liver first for filtering- not back to the heart by its veins. They are called hepatic portal veins. As a result, Liver receives 2 supplies, deoxygenated blood from hepatic portal vein and oxygenated blood from the systemic arteries
Describe the path of blood and passages in the heart from the blood from the systemic circuit coming in
vertically positioned sup. and inf. vena cava receive deoxygenated blood from the systemic circuit which drains into the R atrium + R auricle into the R ventricle. Its pumped to the pulmonary trunk to 2 pulmonary arteries to lungs. It comes back through the two horizontal placed pulmonary veins to drain into the L atrium + L auricle + L ventricle to be pumped to the Aorta - back to the systemic circuit.
Describe the filling phase of the ventricular pump. Whats happening to volume and pressure and position of inlet and outlet valve
The Ventricle is stretching out passively, therefore increasing volume and decreasing pressure. The outlet valve is closed to prevent arterial blood from coming back into the pump and the inlet valve is open to let veinous blood in.
Describe the ejection phase of the ventricular pump. Whats happening to volume and pressure and position of inlet and outlet valve
The ventricle is squeezing inwards actively, therefore volume decreases and pressure increases. the inlet valve is closed to stop blood from going back to the veins and the outlet valve is open to let the blood out
What is the purpose of the atrium
It allows blood to accumulate in the ejection phase behind the closed inlet valve so it can enter quickly during the passive filling phase
How is the pumping capacity increased in the ventricle
The outlet and inlet of the pump lie close together on one side letting the walls of the pumping chamber shorten in length as well as width- more muscle. Adding an auricle continuous with the atrium also increases the amount of blood that can be filled in.
Compare the thickness of Left atrium and Right atrium to the maximum blood pressure
Left atrium max blood pressure is 8 mmHg vs Right atrium max blood pressure 5 mmHg. Both of these have less pressure than ventricles and therefore relatively thin (2-3 mm) with a smooth posterior wall and no inlet valves so pressure can’t be that high. The Left atrium has a higher pressure because the pressure of the blood it receives (pulmonary circuit) is dispersed over a shorter distance than the systemic circuit.
Compare the thickness of Left Ventricle and Right Ventricle to the maximum blood pressure
Left Ventricle max blood pressure is 120 mmHg vs Right Ventricle blood pressure is 27 mmHg. Both pumps pump equal amounts of blood. However Left ventricle has thickest wall because it pumps blood greater distance, to a greater resistance pathway with high pressure. Whereas Right ventricle pumps blood shorter distance in a less resistance pathway.
What are the two atrioventricular valves called and when its open is blood coming in or out
For the left atrioventricular valve it is is tricuspid, and for right atrioventricular valve it is bicuspid (mitral). When open blood is coming in.
How does the structure of two atrioventricular valves help their function
They both have 2 or 3 fibrous connective tissue flaps, with the free end of a flap attached to Chordae Tendinae which are attached to papillary muscles. During Filling, everything is relaxed and blood flows from high pressure in the atria to ventricles. During ejection phase, pressure of blood in the ventricles is higher than atria, pushes the flaps up, closing it and the papillary muscles contract, pulling on the CT to stop the flaps from suddenly flapping backward
Compare the Ratio of peak pressure and Wall Thickness between LV: RV
Peak pressure 5\4: 1
Wall thickness 3:1
What are the two semilunar valves called and when its open is blood coming in or out
There is the Pulmonary valve which lets blood flow out of the Right ventricle and the Aortic valve which lets blood flow out the left ventricle
How does the structure of two semilunar valves help their function
Both valves have 3 cusps that touch meet in the middle but these are not attached to cords because arterial walls are too elastic. Instead they are 3 cups with the bottom of the cup facing the ventricle and the top of the cup facing the artery. This way when pressure in ventricles exceeds the arteries, blood can push the cups to the side to go to arteries, but when the ventricles relax and blood wants to go back, it fills up the cups and closes the opening.
What shape is the pathway taken by blood through the ventricles
V shaped
What is the central cavity in the heart and which holes are bigger: inlet or outlet, why
Central is left ventricle. Inlet holes are bigger than outlet holes because the blood entering in there has lower pressure.
Describe the orientation of the Heart in the body - where can I find it
2/3 of heart mass lies to the left of the midline with 1/3 lying to the right of the midline. The apex of the heart - formed by the tip of the left ventricle and rests of the diaphragm, pointing anteriorly, inferiorly and to the left. The base of the heart is opposite the apex and is formed by the atria.
Describe the borders of the heart : right, inferior, left, superior
Right border: formed by right atrium which has vertical orientation.
Inferior border: formed by right ventricle
Left border: left ventricle
Superior border: blood vessels= base
What are four kind of layers considered part of the Pericardium from inside to outside
Visceral pericardium/Epicardium, Periocardial space filled with pericardial fluid, Parietal Pericardium. Fibrous Pericardium
What is the structure and function of the Serous Pericardium
Delicate membranous sack made of squamous mesothelial cells that secrete serous fluid inside the pericardial cavity to help reduce friction between the parietal and visceral layers as the heart moves
What is the structure and function of the Fibrous Pericardium
It is a layer of of touch, inelastic dense irregular connective tissue that partially fused to the central tendon of the diaphragm. Therefore it helps to prevent overstretching of the heart, provides protection and anchors the heart in the mediastinum.
Describe the structure of Fibrous skeleton of the Heart
Fibrous skeleton is made of dense connective tissue that forms a tricuspid ring around the valves of the heart. There is a complete ring around the Mitral valve (pulmonary to LV) and Aortic valve (LV to systemic) while the Tricuspid (systemic to RV) ring is incomplete and Pulmonary valve (RV to pulmonary) has none. Instead they have Fatty connective tissue in areas where the fibrous skeleton is incomplete.
Describe the mechanical and electrical purpose of Fibrous skeleton of the Heart
They form a structural foundation for the heart valves, preventing overstretching of the valves as blood passes through them. They also serve as a point of insertion for bundles of cardiac muscle fibres and acts as an electrical insulator between the atria and ventricles.
List the 3 stages of conduction system of the heart
- SA node to the atrial muscle
- Atrioventricular node
- Atrioventricular bundle to Purkinje fibres
Describe the speed and result of 1st stage of conduction from the heart
Cardiac excitation occurs at the SA located in the right atrial wall. These are autorhythmic cells that spontaneously depolarise to threshold- acting as a pacemaker. The action potentials triggered from this propogate through both atria through gap junctions in intercalated discs of muscle fibres.
Result : This makes the atria uniform contract at the same time.
Speed: slow
Describe the speed and result of 2nd stage of conduction from the heart
The action potential reaches the AV node located in the interatrial septum and here it slows down because of differences in AV node cell structures. Fibrous skeleton insulates the Action potential elsewhere
Result: 100 m/s delay allowing time for Atria to fill up to the ventricle
Speed: very slow 10x slower than 1st
Describe the speed and result of 3rd stage of conduction from the heart
The action potential goes to the AV bundle located in the interventricular septum, entering the left and right bundles and then to large diameter Purkinje fibres which conduct the action potential from the apex to remaining ventricular myocardium.
Result: Complete and even contraction of ventricles, pushing blood upwards into the arteries (systole)
Speed: Fast 10x 1st
Name the 5 phases of the cardiac cycle in order starting from ventricular filling
Ventricular filling, Atrial contraction, Isovolumetric ventricular contraction, Ventricular ejection, Isovolumetric ventricular relaxation.
Describe the ventricular filling phase of the cardiac cycle:
Ventricular has no systole involved. The ventricle is relaxed, arterial pressure is still very high but outlet valve is closed. Atrium pressure is relatively low and Ventricular pressure is just below the atrium pressure so this causes the inlet valve to open and blood volume to increase to 80% of capacity passivel
Describe the Atrial contraction phase of the cardiac cycle:
SA node depolarises causing Atrial systole. AP goes to the AV node where it is delayed for 100m/s. The pressure in the arteries as slightly decreased and the outlet valve is still closed. The pressure in the atrium has only slightly increased because it has only thin muscular layer and there are no valves to prevent backflow into the veins. This is still sufficient to top up the remaining 20% of blood volume in the ventricle
Describe the Isovolumetric Ventricular contraction phase of the cardiac cycle:
AP goes from AV bundle to Purkinje fibres causing Ventricular systole to start. The ventricular pressure rises rapidly for 0.05 s. As the pressure rises past the atrial pressure but not above the arterial pressure, both of the inlet and outlet valves are closed and the volume doesn’t change.
Describe the Ventricular ejection phase of the cardiac cycle:
Ventricular systole is still continuing. The ventricular pressure exceeds the arterial pressure causing the outlet valves to open quietly and because the blood is ejected faster than it can run off into distributing arteries the pressure of the artery and ventricle rise together to level out at peak pressure (half volume) where the rate of ejection =the rate of run off. After this arterial and ventricular pressures are decreasing as the ventricular volume is gone down to minimum.
All this time, the inlet valve is still closed and blood is starting to fill the atrium.
Describe the Isovolumetric ventricular relaxation phase of the cardiac cycle:
Systole has ended and heart is repolarising. As the ventricle relaxes the ventricular pressure drops rapidly causing the flow direction to reverse as higher pressure arterial blood wants to go back and this causes the outlet valves to close. The ventricular pressure is still not less than atrial pressure so the inlet valve doesn’t open and as a result the volume doesn’t change. This stage is only 0.05 s
What causes the two heart sounds, when do you hear them if you start the cycle at ventricular filling
Two sounds are caused by valves closing at the beginning of the isovolumetric contraction/relaxation phases in both sides of the heart. The first one is a lower frequency sound + longer because of a wider inlet valve cusps closing. The second one is a higher frequency sound + shorter because outlet holes have smaller valve cusps. The sound is split into two, the first being the aortic valve and then pulmonary valve closing because the aortic valve as a higher pressure than pulmonary so wants to close slightly faster
