BISC306 Lecture Notes - Lecture 23: Tunica Media, Blood Vessel, Fetus
11 Apr 2017
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Two ridges on either side of the ventricles; only during systole does it separate into two ventricles h. ii. Can separate different pressures in systemic and pulmonary circulation big advancement. Birds developed 4 chamber heart independent of mammals; so did crocodiles. Can only speculate, but dinosaurs probably had 4 chambered heart. Ancestors of birds, crocodiles, and dinosaurs were probably warm-blooded; so why did crocodiles become cold-blooded: save energy, to stay under water for a very long time and very still need efficient energy use c. Invented cold-blooded to divert less blood to your lungs; for their lifestyle. Coronary blood flow: mammals and birds have a compact myocardium that is well vascularized. The blood is well oxygenated; good because high metabolism b. c. In most fish, amphibians, and reptiles the myocardium is spongy and does not have its own circulation; the blood in the heart chambers serves to perfuse the myocardium; okay because low metabolism.
