J Männer — Page 2 | PubMed Health

PubMed1992

The development of pericardial villi in the chick embryo.

The development of pericardial villi and their relation to the development of the cardiac surface was studied in chick embryos from the 3rd to 10th day of incubation by scanning electron microscopy. During the 3rd day of incubation (stage 14-17 HH) the coelomic epithelium covering the ventral wall of the sinus venosus forms villous protrusions. By the end of the 3rd day (stage 17 HH) these protrusions contact the dorsal wall of the heart, so that a secondary dorsal mesocardium is formed. This bridges the pericardial cavity between the ventral wall of the sinus venosus and the dorsal base of the ventricles. This sinu-ventricular mesocardium exists only temporarily, as on the 8th day of incubation it becomes a part of the cardiac wall due to fusion with the epicardium of the coronary sulcus. During the 4th and 5th day of incubation (stage 17-25 HH), the formation of the epicardium proceeds from the point of attachment of the sinu-ventricular mesocardium. Although these findings suggest that the epithelium of the villous protrusions spreads over the surface of the embryonic heart, one cannot exclude other hypotheses on epicardial origin. The impression of a spreading epicardium could also be created if epicardial cells were to delaminate from a local epithelium in a temporally and spatially organized pattern.

Animals↗

PubMed1990

Developmental aspects of the sinus valves and the sinus venosus septum of the right atrium in human embryos.

In 32 human embryos from 5 to 27 mm of length, stages 13 to 23 (according to the Carnegie system of stages), the contributions of the sinus venosus septum and the right sinus valve of the right atrium to the formation of the Eustachian and Thebesian valve were examined by scanning electron microscopy. The sinus septum takes part in the subdivision of the right sinus valve into the Eustachian and the Thebesian valves. From its first origin the sinus septum forms a septal structure between the orifices of the right hepatic vein (hepatic portion of the inferior caval vein), the precursor of the inferior caval vein, and the left horn of the sinus venosus, the precursor of the coronary sinus. Before the incorporation of the sinus venosus into the right atrium, it has an intra-sinusal position, and extends between the bases of the left and the right sinus valve. During the incorporation of the sinus venosus into the right atrium the sinus septum receives an intra-atrial position, and its positional relationships to the sinus valves and the orifices of the corresponding veins remain unchanged in principle. Due to the connection between the sinus septum and the right sinus valve, after completion of the incorporation of the sinus, the superior portion of the right sinus valve branches y-like into a lateral limb, (i.e. its original inferior portion) and into a medial limb, (i.e. the sinus septum).(ABSTRACT TRUNCATED AT 250 WORDS)

Heart Septum↗