The embryonic heart, though only a simple tube, uses the same basic mechanism to move blood as an adult heart does, new observations in zebrafish suggest.
Adult hearts in vertebrates, such as zebrafish and people, pump blood using valves and muscle contractions to create suction, but the early heart in these animals is a valveless tube.
Nevertheless, this simple organ begins pumping blood when an embryo is just a few days old. Because of its austere anatomy, researchers long assumed that the developing heart uses a mechanism called peristalsis, in which a series of muscle contractions move material from one end of a tube to the other.
"Peristalsis is like squeezing toothpaste out of a tube—if you hold one end and run your fingers down it, the contents will come out," says bioengineer Morteza Gharib of the California Institute of Technology in Pasadena. Peristalsis commonly moves fluids in other parts of the body. For example, in the esophagus, it moves food