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Date Added: 02 / 07 / 2013
Category: English Literature
Words | Pages: 299 | 2
Views: 127

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Essays

View Full Essay Phase     | What is happening?     | What are the valves doing?     | What is the pressure like in the heart chambers?     |
Diastole (Relaxation of the heart)     | First off Blood from the Vena cava (BODY) And the pulmonary veins (Lungs) Enter the Atria. This increases the pressure of the Atria and so causes the Atrioventricular valves to open.¬†Blood enters the ventricles - beware that during this process the Atria and ventricular walls are relaxed. Due to this relaxation of the ventricles this causes the pressure in them to be lower than that of the Aorta and Pulmonary arteries, This in turn causes the Semi-lunar valves of the Aorta and pulmonary arteries to close.     | Semi Luna valves of the aorta and pulmonary artery close.     | Low     |
Atrial Systole (Contraction of the atria)     | After this the atria walls begin to contract this causes the remaining blood left in the Atria to be pushed into the ventricles. The remaining blood in the atria is around 20% of the overall volume of blood in the heart. The muscular walls of the atria are much thinner than those of the ventricles; this is because the blood from the atria has a short distance from the Atria to the Ventricles.     | Semi Luna valves of the aorta and pulmonary artery open.     | High     |
Ventricular Systole (Contraction of the vesicles)     | After a short delay - to allow the ventricles to fill with blood- the ventricular walls begin to contract; this causes the pressure in the ventricles to rise - this in turns causes the Atrioventricular valves to close. With the AV valves closed this causes a further rise in pressure, this causes the Semi-lunar valves of the Aorta and pulmonary arteries to open as blood is forced through them. The left ventricular     | Semi Luna valves of the aorta and pulmonary artery open.     |       |