Date of Award


Document Type

Open Access

Degree Name

Bachelor of Science



First Advisor





looping process, embryo, heart, fetus


Research on fetal cardiac looping is an important because cardiac looping is the first organ to undergo asymmetrical organogenesis. As well, birth defects occur due to errors in the development process, of which congenital heart defects are very common. Most heart defects begin in the looping process that preludes the shape of a mature heart. Therefore, research into heart looping can give light to how these defects develop. The looping process, which occurs between 30 and 56 hours post incubation (stage 10-16 in development), is divided into two processes. The first process, C-looping, is the process where the heart tube, which at first lies along the sagittal at the embryos midline, undergoes dextral rotation and ventral bending to produce a distinct C-shape. Much research has been done on C-looping, as it has been shown C-looping is regulated by factors intrinsic to the heart tube. In S-looping, the atrium moves anterior while the ventricle moves posterior and undergoes dextral rotation, producing the S-shape characteristic of S-looping. Unlike C-looping, little is known about the dynamics behind S-looping. In this thesis, embryonic hearts isolated at stage 12, the stage at the end of C-looping and start of S-looping, were treated with cytochalasin D(CD) and then grown in vitro. The results show that most of the embryos exposed to CD did not develop past stage 12. Using fluorescence microscopy, trademark filamentous actin networks were not present as they are in wild type embryos. Therefore, it is speculated that actin polymerization plays a role in bending of S-looping. Although it has been shown that C-looping relies on factors intrinsic to the heart tube, external factors, such as the effect of the splanchnopleurale membrane, should be research as well since S-looping is a much more complicated process than C-looping. Despite the encouraging results, more data still needs to be obtained to conclude that actin polymerization is essential to S-looping, since low data sets may expose the data to random variation.