Contractile system of the heart in the early development

对胎儿心脏收缩系统进行评价。1)机械功能：对胎儿的收缩功能进行测量，结果表明胎儿早期的肌收缩力小于新生儿。胎儿的心肌收缩依赖于细胞外的钙，而不是细胞内储存部位释放的钙。2)超微结构：电子显微镜显示胎儿肌原纤维稀少，早期胎儿未见肌浆网。3)细胞内钙离子浓度：显微光谱分析显示，早期胎儿细胞内钙离子浓度高于新生儿。

Contractile system of the fetal heart was evaluated. 1) Mechanical function: contractile function was measured and the study showed that the contractile force in the early f etos is less than in the newborn. Myocardial contraction in the fetus is dependent on the extracellular calcium rather than on the calcium released from the intracellular store site. 2) Ultrastructure: electron microscopy revealed that myofibrils are scarce in the fetus and there is no sarcoplasmio reticulum in the early fetus. 3) Intracellular calcium concentration: microspectroscopic examination showed that intracellular calcium concentration in the early fetus is higher than in the newborn.