Hearts and Circulatory Systems summary

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Biological Sciences
Stephen Reid

Hearts and Circulatory Systems The Mammalian Heart The mammalian (and avian) heart consists of two ventricles (left and right) and two atria (left and right). The left ventricle and left atria function as the left heart pumping oxygenated blood to the systemic tissues (systemic circulation). The right ventricle and right atria function as the right heart pumping blood to the lungs (pulmonary circulation). Venous or deoxygenated blood enters the heart from the systemic tissues via the superior vena cava (upper regions of the body) and inferior vena cava (lower regions of the body). Note, although the term deoxygenated blood is often used to refer to venous blood that has left the systemic tissues, venous blood still has a fair amount of oxygen in it (partial pressure of 40 mmHg; 1 mmHg = 1 Torr). Blood flows from the two vena cava into the right atria. From there, blood passes through the tricuspid valve and enters the right ventricle. Blood is pumped from the right ventricle, through the pulmonary artery to the lungs. In the lungs the blood is oxygenated. Blood leaves the lungs with a partial pressure of approximately 100 mmHg. Blood from the lungs flows back to the heart via the pulmonary vein. The pulmonary vein enters into the left atria. From the left atria blood flows through the bicuspid valve into the left ventricle. Blood is then pumped from the left ventricle, through the aorta, to the systemic tissues. The blood delivers oxygen (and other nutrients to the tissues) while picking up carbon dioxide and other metabolic waste products. The blood leaving the systemic tissues(now called deoxygenated blood) travels through veins and ultimately ends up in the vena cava and the cycle starts over. Note, in almost all circumstances, arteries carry oxygenated blood and veins carry deoxygenated blood. However, the pulmonary artery carries deoxygenated blood from the heart to the lungs while the pulmonary vein carries oxygenated blood from the lungs to the heart. This terminology is used because arteries take blood away from the heart and veins return blood to the heart. The mammalian heart essentially functions as two separate hearts that function in parallel. The left heart pumps oxygenated blood to the tissues while the right heart pumps deoxygenated blood to the lungs. Teleost (Bony) Fish Heart and Circulation www.notesolution.com
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