20081013 - Lecture 18 Cardiovascular page#1 Lecture18...

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Lecture 18 Cardiovascular page #1 Lecture18 Coronary circulation: nutrients and oxygen carried to heart muscle to meet aerobic demand. Certain fishes and amphibians can obtain nutrients and oxygen for the inner muscle tissues of the heart from the blood coursing through the chambers. Outer layers still need blood vessels. Adenosine Æ coronary artery flow with activity and decrease heart rate (conserves energy. Sympathetic stimulation Æ coronary flow secondary to adenosine. Pericardium: sac surrounding the heart; fibrous connective tissue. The inner layer is double - one layer forms the outer layer to heart, the other is the inner layer of the pericardial sac. Serous fluid is secreted into the double walled inner layer, lubricating the outside of the heart and decreasing friction. The pericardium of elasmobranch sharks, lungfishes and some crustaceans and mollusks is cartilaginous - rigid. When ventricle contracts, negative pressure is generated in the pericardial chamber, which aspirates venous blood. Mammals, birds, amphibians and bony fishes have a compliant pericardium. Shark heart
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Lecture 18 Cardiovascular page #2 Comparative functional morphology of vertebrate hearts Birds and mammals have two series of heart chambers in parallel. This permits a lower pressure in the pulmonary circulation. The high pressure in the systemic is advantageous Æ transit times and ↑Δ blood flow. Disadvantage – CO must be the same by both sides of the heart independent of the requirements of the two circuits. lungfishes, amphibians, reptiles, bird embryos, fetal mammal embryos have mechanisms for shunting blood from one circuit to the other – usually right to left because of low gas exchange in lung. fishes Respiratory and systemic circulations are in series. There is higher ir-breathing fishes: upplements oxygen taken up by gill. Usually a structure other than gills pressure in the gills than in the systemic system.
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20081013 - Lecture 18 Cardiovascular page#1 Lecture18...

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