the heart Flashcards
Right side of the heart.
Deoxygenated blood enters the right side of the heart from the vena cava. It is then pumped to the lungs via the pulmonary arteries to pick up oxygen.
Left side of the heart.
Oxygenated blood enters from the lungs via the pulmonary veins, and is then pumped around the body via the aorta to deliver oxygen to the cells.
Why does the blood in the two sides of the heart not mix?
- The right hand side has deoxygenated blood, the left hand side has oxygenated blood.
- The 2 sides operate under different pressures.
What is the role of coronary arteries?
- These supply the cardiac muscle cells with oxygenated blood and glucose - so that they can respite - to produce ATP - to allow the cells to keep contracting and relaxing.
What happens if you have a blocked artery?
- It can be fatal e.g heart attacks and stroke.
What do the atrioventricular valves link?
- The atria to the ventricles.
What do the semi-lunar valves link?
The ventricles to the pulmonary artery and aorta.
Why do the atria have thinner walls than the ventricles?
The atria only have to generate enough pressure to force blood down into the ventricles, which is a very short distance. Does not require a thick muscle wall.
Why does the left ventricle have a thicker wall than the right ventricle?
Left ventricle has to generate enough pressure to force the blood up into the aorta around the whole body. A lot of muscle is needed to create enough force to overcome resistance of these vessels. Right ventricle only has to pump blood to the lungs, a shorter distance, so less force is needed and muscle does not need to be as thick.
What are the three stages of the cardiac cycle?
1 - atrial systole
2 - ventricular systole
3 - diastole
What happens during atrial systole?
- ventricles are relaxed.
- atria contract, decreasing volume of the chambers and increasing pressure inside the chambers
- this pushes blood into the ventricles through atrioventricular valves
- slight increase in ventricular pressure and chamber volume as ventricles receive blood from contracting atria
What happens during ventricular systole?
- atria relax
- ventricles contract decreasing their volume, increasing their pressure
- pressure becomes higher in the ventricles than the atria, which forces the av valves shut to prevent back flow
- pressure in ventricle is higher than in the aorta and pulmonary artery, which forces open the semi lunar valves and blood is forced out of these arteries.
What happens during diastole?
- Ventricles and atria both relax.
- Higher pressure in the pulmonary arteries and aorta closes the SL values the prevent back flow from the ventricles.
- Blood returns to the heart and the atria fill again due to higher pressure in the vena cava and pulmonary vein.
- This starts to increase pressure of the atria.
- As ventricles relax, their pressure falls below pressure of atria and so AV valves open. This allow blood to flow passively into ventricles from the atria. Atria contracts and process begins again.
Why is it important that there is a slight delay between the atria contracting and ventricles contracting?
To allow time for the blood to flow down into the ventricles from the atria, before the ventricles contract.
Why is it important that ventricles empty from the base?
To ensure that all of the blood is squeezed upwards towards the arteries, to leave the heart.
