Heart anatomy and cardiac cycle Flashcards
What is the pericardium?
Sac surrounding the heart.
Has an inner visceral layer (epidcardium) that is continuous with the surface of the heart and an outer parietal layer.
Describe the position of the left atrium
At the back and in the middle
It is situated under the tracheal bifurcation (this has clinical importance)
What is the fibrous cardiac skeleton? What is its function?
- Fibrous cardiac skeleton separates atria and ventricles
- Serves as electrical insulation; ensures the only way impulses can pass through to ventricles is via the AV node
Describe the structure of cardiomyocytes
- Large, cylindrical cells
- Striated
- Central nucleus
- They form a functional electrical syncytium (can work as a unit)
- Have intercalacted discs; gap junctions where electrical coupling can occur
- Highly metabolically active so have many mitochondria
Explain the response to injury by cardiomyocytes
- Cannot regenerate if damaged
- Skeletal muscle cells use satellite cells to regenerate after damage, however cardiomyocytes do not have these
- Ongoing area of stem cell research
What stage of the cardiac cycle does this show? Describe what is going on and any sounds that may be heard.
Atrial systole
- Walls of the atria contract, pushing the remaining blood from the atria into the ventricles
- Semilunar valves are closed
- The ventricles fill with blood
- S4 may be heard here, if blood strikes a non-compliant left ventricle
What stage of the cardiac cycle does this show? Describe what is going on and any sounds that may be heard.
Ventricular systole
- This encompasses the phases isovolumetric contraction and rapid and reduced ejection
- Walls of ventricles contract, increasing ventricular pressure
- When this is higher than pressure in the atria, the AV valves close
- This produces S1 - “LUB”
- The pressure in the ventricles ncreases until it exceeds the pressure in the outgoing arteries
- The semilunar valves open and blood flow into the outgoing arteries
- Atria start to refill as they collect bloodfrom veins
What stage of the cardiac cycle does this show? Describe what is going on and any sounds that may be heard.
(Ventricular) diastole
- This encompasses the phases isovolumetric relaxation, rapid filling and diastasis
- The ventricles relax
- The pressure in the ventricles becomes lower than in the outgoing arties
- The semilunar valves close, producing S2 - “DUB” and preventing the backflow of blood into the ventricles
- When the pressure in the ventricles falls below the pressure in the atria, the AV valves open
- Blood flows from the atria into the ventricles
What stage of the cardiac cycle does this show? Describe what is going on and any sounds that may be heard.
Start of the cardiac cycle
- Phase = diastasis, when both atria and ventricles are in diastole
- The AV valves are open and blood is flowing passively into the ventricles
- S3 may occur here, if blood strikes a compliant left ventricle
(ventricular) Systole
time between the onset of S1 and the onset of S2
Diastole
the time between the onset of S2 and the onset of S1
The red line represents the pressure in the _______ over the course of a cardiac cycle
aorta
The blue line represents the pressure in the ____________ over the course of a cardiac cycle
left ventricle
The green line represents the pressure in the _________ over the course of a cardiac cycle
Left atrium
What does the purple line represent?
When will you hear S1 - A,B,C or D?
B - when the AV valves close
When will you hear S2 - A,B,C or D?
C - when the semilunar valves close.
1
Great vessels
2
Visceral pericardium (=epicardium)
3
Pericardial cavity (exaggerated in size)
4
Parietal pericardium
5
Fibrous pericardium
6
Mediastinal pleura
7
Sternopericardial ligament
