Interventricular septum (IS) has been studied in ordinary formed human fetal hearts (20–28 weeks) by means of the anatomo-metrical method. VS breadth appears to be less than its length, but is more than the breadth of the medial walls of both ventricles. The outlet length surpasses the inlet one more on the right than on the left septal side. On transversal sections the angle between IS departments is 122 — 139°. The angle degree increases from the basis to the apex of the heart. The angle between the longest axes of the right surface divisions is 38 — 42°. The length proportions of the IS departments become constant to the middle fetal period. The sinus part of the IS is square or multiangular (often four- or five-angular) and along the bloodstream. The development of the sinus part is coordinated with formation of the inlet trabecular part. The conal part is the smallest one. The conal development in the middle fetal period has not been completed yet. Size proportions of the IS parts and departments seem to be much the same in the normal fetal and newborn hearts.
A.A. Yakimov Structure Of Muscular Parts of Interventricular Septum of the Heart Human Fetal // Saratov Journal of Medical Scientific Research, Vol. 5, Issue 2, 2009, pp. 155-159