Provided video explains the formation of interatrial septum in sufficient details along with some clinical correlates that are relevant to it. Timeline: 0:00 - Introduction 0:34 - Review of the heart tube 1:05 - Formation of septum intermedium and septum spurium 3:19 - Formation of septum primum and ostium primum 5:10 - Formation of ostium secundum and septum secundum 6:50 - Foramen ovale 7:37 - Closure of foramen ovale 9:25 - Defects of the interatrial septum