I. Development of the Heart

GLOSSARY
arrhythmia general term for an irregularity or rapidity of the heartbeat, an abnormal heart rhythm.
caudal pertaining to toward the tail or distal end of the body.
cephalic pertaining to the head or to the head end of the body.
blastula usually spherical body produced by cleavage of a fertil¬ized ovum, consisting of a single layer of cells (blastoderm) surrounding a fluid-filled cavity (blastocele).
embryo developing human from conception until the end of the 8th week by which time all organ systems have been formed.
ischemic heart disease atherosclerosis (atheromatous plaques) causes obstruction to coronary arteries depriving the myocar¬dium of blood containing oxygen and necessary nutrients.
karyotype chromosomal characteristics of an individual or cell line.
myocardium the heart muscle.
IT IS NOT WIDELY KNOWN THAT IN THE HUMAN embryo, the unique little heart begins to beat as early as day 22. Further research in cardiovascular embryology is crucial to the understanding of different cardiac anomalies and the development of therapeutic and preventive strategies.

• I. DEVELOPMENT OF THE HEART
  Commitment to the cardiogenic cell lineage occurs early in development soon after gastrulation (the embryonic state following the blastula), approximately 48 h follow¬ing fertilization. The molecular basis for the formation of cardiac myocytes from the presumptive mesoderm requires further elucidation. The mesoderm consists of three germ layers that are incorporated in the building of the tissues and organs of the embryo. Cells committed to the cardiac
• BIBLIOGRAPHY
  Friedman, W. F., and Silverman, N. Congenital heart disease in infancy and childhood. In Heart Disease, sixth edition. E. Braunwald, D. P. Zipes, and P. Libby, eds. W. B. Saunders, Philadelphia, 2001.

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