Component 2.23 Exam Q Flashcards
label, blue = deoxygenated, red = oxygenated
aorta
C and D
E
A B F
atria vs ventricle location
The atria are at the top of the heart and the ventricles at the bottom
heart valves names
Between the ventricles and atria are valves to prevent backflow. These valves are the atrioventricular valves, the right one is the tricuspid (we always ‘tri’ to be right) and the left is the bicuspid or mitral valve. Blood enters the heart from the vena cava and pulmonary veins into the atria and then is pushed through to the ventricles as the atria contract.
movement of blood and valves
When the ventricles contract, the atria are relaxed. The blood is pushed out through the aorta and pulmonary arteries at the top of the heart. The atrioventricular valves are forced shut to prevent backflow to the atria and the chordae tendineae (heart strings) prevent the valves turning inside out. At the base of the two arteries are semi-lunar valves, the aortic valve at the base of the aorta and the pulmonary valve at the base of the pulmonary artery. When the ventricle relaxes, the semi-lunar valves fill with blood and close preventing backflow from the arteries to the ventricles.
diagram of heart labelled
A
B
heart pressure
Blood flows from atria to ventricles and then to arteries because of pressure generated by contraction of the heart muscle. Movement is from high to low pressure. As blood enters an artery, the pressure increases in the vessel; backflow to the ventricles is prevented by the closure of the semi-lunar valves.
Conventionally the blood flow is described as starting with the atria contracting – atrial systole. When the atria contract the pressure in the atria is higher than that in the ventricles and blood is pushed through the open atrioventricular valves into the ventricles. At this point, the ventricles are relaxed (in diastole).
When the ventricles are full, they contract from the apex upwards. The pressure in the ventricles increases rapidly and quickly exceeds that of the atria, pushing the atrioventricular valves shut.
The pressure is raised above that of the arteries and the semi-lunar valves are forced open. Blood is pushed upwards and into the arteries.
As the ventricles relax, the pressure falls below that in the arteries. The semi-lunar valves fill with blood and close, preventing blood flowing backwards into the ventricles. The pressure in the ventricles continues to drop until it is below that of the atria, blood flows from the veins through the atria and the ventricles start to fill. The heart is in diastole.
The atria contract… and the whole process starts again.
The valves closing make the characteristic lub-dub heart sounds.
graph pressure and valves atria ateries and ventricles
describe interval A
During time interval A, the atria are contracting increasing the atrial pressure. The ventricles are relaxed and the pressure in the ventricles is lower than the atrial pressure. The slight increase in pressure in the ventricles is because blood is being pushed into the ventricles.
describe interval B
During time interval B, the pressure in the ventricles increases as the ventricles contract. The pressure in the ventricles rises above that of the atria at 0.2 seconds and the atrioventricular valves close. At 0.24 seconds the pressure in the ventricles rises above the arterial pressure and the semi-lunar valves open.
describe interval C
During time interval C, the ventricular systole causes blood to enter the arteries and the pressure in the arteries rises. As the ventricles start to relax, the pressure falls until, at 0.56 seconds, the pressure in the ventricles falls below that in the arteries, the semi-lunar valves fill with blood and close.
describe interval D
During time interval D, the ventricles continue to relax, and all heart valves are closed. At 0.6 seconds, the pressure in the ventricles falls below that of the atria and the atrioventricular valves open.
describe interval E
During time interval E, the heart is in diastole, the atria and ventricles are relaxed and blood flows from the veins, through the atria and into the ventricles, causing a slight increase in pressure as the ventricles begin to fill.
