the heart develops and begins pumping blood by week 4 of development.
the heart develops and begins pumping blood by week 4 of development.
when does the heart develop and begin pumping blood?
by week 4 of development
Na
Na
avian hearts are generally larger than mammalian hearts when compared to body mass. this adaptation allows more blood to be pumped to meet the high metabolic need associated with flight. birds, like the flamingo, have a very efficient system for diffusing oxygen into the blood; birds have a ten times greater surface area to gas exchange volume than mammals. as a result, birds have more blood in their capillaries per unit of volume of lung than a mammal. the american flamingo's four-chambered heart is myogenic, meaning that all the muscle cells and fibers have the ability to contract rhythmically. the rhythm of contraction is controlled by the pace maker cells which have a lower threshold for depolarization. the wave of electrical depolarization initiated here is what physically starts the heart's contractions and begins pumping blood. pumping blood creates variations in blood pressure and as a result, creates different thicknesses of blood vessels. the law of laplace can be used to explain why arteries are relatively thick and veins are thin.
american flamingo