What paths does blood take through the heart?
Refer to Figure 8.25 as you read.
1 Deoxygenated blood from various parts of the body is returned to the right atrium. Blood from the head, neck and arms is returned to the right atrium by a large vein called the anterior or superior vena cava. Blood from the other parts of the body (excluding the lunge) is brought back by the posterior or inferior vena cava.
2 When the right atrium contracts, blood flows into the right ventricle. Between the right atrium and the right ventricle is the tricuspid valve, which opens when the pressure in the right ventricle becomes lower than the pressure in the right atrium. It consists of three flaps. These flaps are attached to the right ventricle by cord-like tendons called chordae tendineae. They point downwards to permit easy flow of blood from the atrium into the ventricle.
3 When the right ventricle contracts, the blood pressure forces the flaps of the tricuspid valve to close. This prevents backflow of blood into the atrium. The chordae tendineae prevent the flaps from begin reverted into the atrium when the right ventricle contracts. Blood leaves the right ventricle through the pulmonary arch. The pulmonary arch leaves the heart and divides into pulmonary arteries, one to each lung. Semi-lunar valves in the pulmonary arch prevent backflow of blood into the ventricle.
4 The blood in the pulmonary arteries is at lower pressure than the blood in the aorta. This slows down the rate of blood flow to give more time for gaseous exchange in the lungs.
5 Oxygenated blood from the lungs is brought back to the left atrium by the pulmonary veins. When the left atrium contracts, the blood pressure in the left atrium becomes higher than that in the left ventricle. This causes the bicuspid valve to open and blood enters the left ventricle. The bicuspid valve or mitral valve separates the left atrium from the left ventricle. This similar in structure and function to the tricuspid valve except that it has two flaps instead of three. When the left ventricle contracts, blood leaves through a large artery, the aortic arch.
6 From the aortic arch, blood distributed to all parts of the body (except the lunge). Even the coronary arteries, which supply has muscles with food and oxygen, originate in the aortic arch. The aortic arch curves upwards from the ventricle as a U-shaped tube. It also possesses semi-lunar valves to prevent backflow of blood into the left ventricle. Blood entering the aorta is at a very high pressure.
7 Two small coronary arteries emerge from the aortic arch (Figure 8.24a). They bring oxygen and nutrients to the heart muscles.
What paths does blood take through the heart?
Refer to Figure 8.25 as you read.
1 Deoxygenated blood from various parts of the body is returned to the right atrium. Blood from the head, neck and arms is returned to the right atrium by a large vein called the anterior or superior vena cava. Blood from the other parts of the body (excluding the lunge) is brought back by the posterior or inferior vena cava.
2 When the right atrium contracts, blood flows into the right ventricle. Between the right atrium and the right ventricle is the tricuspid valve, which opens when the pressure in the right ventricle becomes lower than the pressure in the right atrium. It consists of three flaps. These flaps are attached to the right ventricle by cord-like tendons called chordae tendineae. They point downwards to permit easy flow of blood from the atrium into the ventricle.
3 When the right ventricle contracts, the blood pressure forces the flaps of the tricuspid valve to close. This prevents backflow of blood into the atrium. The chordae tendineae prevent the flaps from begin reverted into the atrium when the right ventricle contracts. Blood leaves the right ventricle through the pulmonary arch. The pulmonary arch leaves the heart and divides into pulmonary arteries, one to each lung. Semi-lunar valves in the pulmonary arch prevent backflow of blood into the ventricle.
4 The blood in the pulmonary arteries is at lower pressure than the blood in the aorta. This slows down the rate of blood flow to give more time for gaseous exchange in the lungs.
5 Oxygenated blood from the lungs is brought back to the left atrium by the pulmonary veins. When the left atrium contracts, the blood pressure in the left atrium becomes higher than that in the left ventricle. This causes the bicuspid valve to open and blood enters the left ventricle. The bicuspid valve or mitral valve separates the left atrium from the left ventricle. This similar in structure and function to the tricuspid valve except that it has two flaps instead of three. When the left ventricle contracts, blood leaves through a large artery, the aortic arch.
6 From the aortic arch, blood distributed to all parts of the body (except the lunge). Even the coronary arteries, which supply has muscles with food and oxygen, originate in the aortic arch. The aortic arch curves upwards from the ventricle as a U-shaped tube. It also possesses semi-lunar valves to prevent backflow of blood into the left ventricle. Blood entering the aorta is at a very high pressure.
7 Two small coronary arteries emerge from the aortic arch (Figure 8.24a). They bring oxygen and nutrients to the heart muscles.
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