Much of what we know about the embryonic circulation Is derived from studies of the chick embryo (Clark and Hu 1982). The similarities between the chick, rat (Nakazawa 1988) and fetal lamb (Kirkpatrick 1976) suggest that, while the details of functional change may vary, common mechanisms are expressed In these animal groups (Nakazawa 1988). Some of the mechanisms that control the cardiovascular system in the mature animal are expressed early In development (Clark 1990). The primary determinants of cardiovascular function in the embryo as in the mature animal are preload, afterload, heart rate and myocardial contractility. These factors regulate cardiac output before the development of the functioning autonomic nervous system. The Frank-Starling relationship Is operative and effective in both the fetal lamb heart (Kirkpatrick 1976) and the chick embryo (Wagman 1990). After maturation of the autonomic nervous system, both the parasympathetic and sympathetic systems control cardiovascular function in the fetal lamb (Nuwayhid 1975).

, , , ,
National Institute of Health, SCaR In Pediatric Cardiovascular Disease (University of Rochester)
J.W. Wladimiroff (Juriy)
Erasmus University Rotterdam , Eburon Academic Publishers, Delft
Erasmus MC: University Medical Center Rotterdam

Ursem, N. (1999, March 31). Heart Rate and Blood Flow Velocity Variability in the Human Fetus. Retrieved from