Morse D E, Rogers C S, McCann P S
J Submicrosc Cytol. 1984 Apr;16(2):259-72.
Septum primum of the chick and rat heart develops as a solid, crescentic fold on the inner atrial wall. In the chick this septum forms during days 3 and 4 of incubation. The same septum begins development during day 12 in the rat. In both species the septum grows rapidly toward the two endocardial cushions, decreasing the size of foramen primum in the process. A second foramen, foramen secundum, develops in the septum primum to maintain an interatrial shunt. Multiple foramina form in the middle and dorsal portions of the chick septum primum. These foramina continue to form until the middle of the second week of incubation. Prominent rounded cells are abundant on the chick septum in the region of foramina formation. These cells are no longer demonstrable when new foramina cease to be formed. At the time of hatching the cords of tissue separating foramina have thickened and fewer foramina exist. By day 2 after hatching the septum is an imperforate partition. The septum is seen to protrude into the left atrium, even after hatching. Foramen secundum forms very rapidly in the rat. Scanning electron microscopy indicates that it develops initially as multiple perforations which quickly coalesce into one aperture in the middle and ventral portions. The rat has a septum secundum which develops just to the right of septum primum. The valves of the sinus venosus project into the right atrium of the rat heart. Nodules are prominent features of the right valve early during the third week of gestation.
鸡和大鼠心脏的原发隔是在心房内壁上形成的一个坚实的新月形褶皱。在鸡中，这个隔在孵化的第3天和第4天形成。在大鼠中，同一个隔在第12天开始发育。在这两个物种中，隔都迅速向两个心内膜垫生长，在此过程中使原发孔的大小减小。在原发隔中形成了第二个孔，即继发孔，以维持心房分流。在鸡的原发隔中部和背侧形成多个孔。这些孔一直形成到孵化第二周中期。在鸡原发隔形成孔的区域有大量突出的圆形细胞。当新的孔不再形成时，这些细胞就不再可见。在孵化时，分隔孔的组织索增厚，孔的数量减少。孵化后第2天，隔成为一个无孔的分隔。即使在孵化后，也能看到隔突入左心房。继发孔在大鼠中形成得非常迅速。扫描电子显微镜显示，它最初以多个穿孔的形式出现，这些穿孔很快在中部和腹侧合并成一个孔。大鼠有一个继发隔，它在原发隔的右侧发育。静脉窦瓣突入大鼠心脏的右心房。在妊娠第三周早期，结节是右瓣的突出特征。
