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Embryonic development of the heart. I. A light and electron microscopic study of myocardial development in the early chick embryo
Author(s) -
Manasek Francis J.
Publication year - 1968
Publication title -
journal of morphology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 74
eISSN - 1097-4687
pISSN - 0362-2525
DOI - 10.1002/jmor.1051250306
Subject(s) - myofibril , embryonic heart , golgi apparatus , cytoplasm , biology , endoplasmic reticulum , microbiology and biotechnology , organelle , embryonic stem cell , electron microscope , sarcomere , embryo , lipid droplet , ultrastructure , glycogen , anatomy , myocyte , embryogenesis , intracellular , biochemistry , physics , optics , gene
Embryonic chick myocardium (stages 8+ to 12−) was studied by light and electron microscopy. The myocardium, which is initially comprised of radially oriented cells with large intercellular spaces gradually becomes more tightly packed. Intercellular spaces decrease and the cells assume a circumferential orientation. Myocardial cells remain epithelial throughout formation of the functional tubular heart and specialized epithelial junctions (apical junctional complex or terminal bars) undergo modification to form intercalated discs. Embryonic myocardial cells contain large amounts of free ribosomes and particulate glycogen, the latter often associated with portions of granular reticulum. Unlike developing skeletal muscle. The amount of granular reticulum contained in the myocardial cell cytoplasm is large and, along with a hypertrophied Golgi apparatus, suggests that these cells may have a secretory function. These organelles persist during the initial period of fibril formation. Myofibrils apparently form from non filamentous precursor material and not by alignment of sequentially synthesized components.