6.1 The Heart Flashcards
The heart is…
A muscular organ which pumps blood continuously around the body
Divided into…
Two halves: left & right, each half acts as a separate pump
Right side of the heart…
Receives deoxygenated blood from the body via the vena cava
Deoxygenated blood enters…
The right atrium, pushed into the right ventricle, pumped to the lungs via the pulmonary arteries.
Simultaneously, oxygenated blood (from the lungs) returns to the left atrium via the pulmonary veins. It is pushed from the left atrium into the left ventricle, from where it is pumped around the body via the aorta.
Walls of the atria are…
Relatively thin and elastic - do not have a lot of muscle as they do not need to generate much pressure to pump blood to the ventricles
Ventricles have…
Much thicker, muscular walls to generate a higher pressure to pump blood to the lungs and body.
Valves in the heart…
Prevent back flow of blood
Atrioventricular valves lie…
Between the atria and the ventricles Stop blood flowing back from the ventricles into the atria
Have strong fibres (tendinous cords) to stop them turning inside out
Semilunar valves…
Stop blood flowing back into the ventricles from the pulmonary artery and the aorta
1st stage of cardiac cycle:
•Diastole
Blood enters atria and ventricles from pulmonary veins and vena cava
Semi-lunar valves closed
Left & right AV valves open
Relaxation of ventricles draws blood from atria
2nd stage of cardiac cycle:
•Atrial Systole Atria contact to push remaining blood into ventricles Semilunar valves closed Left & right AV open Blood pumped from atria to ventricles
3rd stage of cardiac cycle:
•Ventricular systole Blood pumped into pulmonary arteries and aorta Semilunar valves open Left & right AV closed Ventricles contact
Diastole is:
Heart muscle is relaxed
Deoxygenated blood enters the right atrium from the vena cava and oxygenated blood enters the left atrium via pulmonary veins
As atria fill with blood - atria pressure rises, pushes the AV valves open and allows blood to pass into ventricles
Atrial systole is:
Walls of atria contract
Pushes the remaining blood in the atria into the ventricles
Force of the atria contraction pushes the AV valves wide open
Ventricular systole:
Ventricle walls contract
Increases the pressure inside the ventricles
Pressure in the ventricles forces semilunar valves in the pulmonary artery and the aorta to open
Blood forced out of ventricles towards the lungs and around the body
