In its classic definition, by FranÃ§ois-Louis Ganshof (1944), feudalism describes a set of reciprocal legal and military obligations among the warrior nobility revolving around the three key concepts of lords, vassals and fiefs.
The exact cause of intracardiac echogenic foci remains unclear; however, they appear to be caused by small deposits of calcium in the papillary muscle of the fetal heart.
One hypothesis is that the central administration of 5-HT can cause bradycardia or tachycardia and hypo- or hypertension mediated by activation of 5-HT1A and 5-HT2 receptors. Another hypothesis suggests that alpha1-adrenegic antagonism with peripheral vasodilatation causes postural hypotension and compensatory tachycardia.