Early Development, Devel. Physiol., Dr. D. Penney

Table 2.05 - Phases of Heart Development from a Cellular Point of View:

  • Primary Hyperplastic Phase - In early development nearly all cells (75% - 90%) are myocardial cells, and increase in heart size occurs through increase in number of myocardial cells, but no increase in cell size. Connective tissue cells increase in number.

  • Transitional Phase - In late fetal or early neonatal development mitotic division of myocardial cells slows and organ growth occurs by both hyperplasia and hypertrophy. Connective tissue, endothelial, and smooth muscle cells continue to increase in number, but not in size.

  • Hypertrophic Phase - Postnatal heart growth to adulthood occurs solely by hypertrophy of myocardial cells, while connective tissue, and other cells continue to increase in number but not in size.

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