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Because there are crescent shaped, like half moons :)

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What two blood vessels contain semilunar valves?

Right at the very start of the aorta is the aortic valve and at the very start of the pulmonary artery is the pulmonart valve, each of which are semilunar. In the heart there are two semilunar valves that lad to blood vessels. The pulmonary semilunar valve leads to the pulmonary trunk, and the Aortic semilunar valve leads to the Aorta.


The second heart sound results from vibrations generated by the .?

closing of the semilunar valves at the start of diastole


During the isovolumetric relaxation phase of the cardiac cycle the AV valves are and the semilunar valves are?

During the isovolumetric relaxation phase of the cardiac cycle, the AV valves (mitral and tricuspid) are closed to prevent backflow of blood into the atria while the muscle fibers relax. The semilunar valves (aortic and pulmonary) are also closed to prevent blood from flowing back into the ventricles as they start to relax.


What happened to the heart?

Blood first enters the atria by the veins. The walls of the atria contract, pushing blood from the atria into the ventricles through the atrioventricular valves, which are open at that time. The semilunar valves are therefore closed, so that the ventricles can fill with blood. The walls of the ventricles then contract powerfully and the blood pressure rapidly rises inside them. This first causes the atrioventricular valves to close in order to prevent back-flow of blood to the atria and then causes the semilunar valves to open, allowing blood to be pumped out into the arteries. At the same time this is occurring, the atria start to refill with blood collected from the veins. The ventricles stop contracting and as pressure falls inside them the semilunar valves close, preventing back-flow of blood from the arteries to the ventricles. When the ventricular pressure drops below the atrial pressure, the atrioventricular valves open. Blood entering the atrium from the vains then flows on to start filling the ventricles once again.


What are some words that start with ao?

aorta


Where does circulation start?

This system begins at the left side of the heart and through the aorta.


What is the function of the chords attached to the valve flaps between the atria and the ventricle?

These chords are called the Chordea Tendinae. Their function is to stop the valves from invertung back into the atria. If they weeken and stretch they start to allow the valves to be pushed back into the atria, this is called floppy valve syndrome.


What is 3 body parts that start with a?

alimentary canal, adrenal gland, aorta, arteries


What are signs of a belt jumping time on a 2003 Chrysler Sebring?

Check engine light, low power, no start, runs rough, bent valves,Check engine light, low power, no start, runs rough, bent valves,


What car parts start with the letter V?

Valves


5 letter words that start and end with the letter A?

* alpha * amnia * aorta * areca * arena * aroma * atria


Explain the events that occur during each of the three phases of the cardiac cycle?

Relaxation period: this beings at the end of a cardiac cycle when the ventricles start to relax and all four chambers are in diastole. Repolarization of the ventricle muscle fibers initiates relaxation and pressure within them drops. When ventricular pressure drops below atrial pressure, the AV valves open and ventricular filling beings.Atrial systole (contraction): an action potential from the SA node causes atrial depolarization. Atrial contraction follows the P wave, which marks the end of the relaxation period. As the atria contact, they force the last 25% of the blood into the ventricles. At the end of the atrial systole, each ventricle contains about 130 mL of blood. The AV valves are still open and the semilunar valves are still closed.Ventricular systole (contraction): pushes blood against the AV valves, forcing them shut. As ventricular contraction continues, pressure inside the chambers quickly rises. When left ventricular pressure surpasses aortic pressure and right ventricular pressure rises above the pressure in the pulmonary trunk, both semilunar valves open and ejection of blood from the heart begins. Ejection continues until the ventricles start to relax. At rest, the volume of blood ejected from each ventricle during the ventricular systole is about 70 mL.