Heart, blood vessels and blood

• Oxygenated blood from the lungs enters the left atrium via the pulmonary vein
• Blood passes into the left ventricle before being pumped out through the aorta. The wall is very thick and muscular to generate the high pressure required to pump the blood around the whole body
• Deoxygenated blood in the vena cava passes into the right atrium, it is under low pressure
• Blood passes into the right ventricle before being pumped out into the pulmonary artery going to the lungs
• The atrio ventricular valve prevents blood from flowing backwards when the blood underneath it exerts a high pressure causing it to stay shut
• The semi lunar valve prevents blood from flowing backwards into the ventricles when they relax in the cardiac cycle
• The septum separates the two sides of the heart, this is where a hole in the heart can exist resulting in mixing of oxygenated and deoxygenated blood
• The tendinous chords insert into the ventricle wall, are very tough and prevent the valves from turning inside out
• Cardiac muscle cells will contain numerous mitochondria to provide energy. The cells are myogenic (contraction is self initiated)
• The coronary artery is the first branch of the aorta, it provides oxygenated blood to the cardiac muscle
• Blood in the pulmonary vein from the lungs enters the left atrium when its muscular walls are relaxed.
• The walls of the atrium then contract, forcing blood into the left ventricle.
• At this point the walls of the left ventricle are relaxed but they will then contract, the volume in the left ventricle increases, creating high pressure so blood is forced upwards.
• This causes the atrio ventricular valves to close and the semi lunar valves to open.
• This allows the blood to pass into the aorta to be transported around the body.
• The blood transports oxygen and glucose to the cells of the body for aerobic respiration.
• Deoxygenated blood returns to the heart in the vena cava.
• The blood enters the right atrium and the chamber's walls are relaxed.