. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. HISTOGENESIS OF NON-STRIATED MUSCULAR TISSUE J95 fibrils that are at first varicose, but later become of uniform caliber. Fine fibrils (/./) which are homogeneous from the first, make their appearance after the coarse ones and in some cases seem to be formed by the splitting of the latter. They are scattered uniformly throughout the cytoplasm of the muscle cells and increase in number as development proceeds, while the coarse fibrils diminish and may be entirely wanting in the adult tissue. S
. The development of the human body : a manual of human embryology. Embryology; Embryo, Non-Mammalian. HISTOGENESIS OF NON-STRIATED MUSCULAR TISSUE J95 fibrils that are at first varicose, but later become of uniform caliber. Fine fibrils (/./) which are homogeneous from the first, make their appearance after the coarse ones and in some cases seem to be formed by the splitting of the latter. They are scattered uniformly throughout the cytoplasm of the muscle cells and increase in number as development proceeds, while the coarse fibrils diminish and may be entirely wanting in the adult tissue. Some of the mesenchyme cells in each muscle sheet fail to undergo the differentiation just described and multiply to form the interstitial connective tissue, which usually divides the mus- cle cells into more or less dis- tinct bundles. Traces of the original syncytial nature of the tissue are to be seen in the intercellular bridges that occur between the non-striated muscle cells of many adult forms. The cells from which the heart musculature develops are at first of the usual well defined embryonic type, but, as development proceeds, they become irregularly stellate in form, the processes of neighbor- ing cells fuse and, eventually, there is formed a continuous mass of protoplasm or syncytium in which all traces of cell bounda- ries are lacking (Fig. 118). While the individual cells, or myoblasts as they are termed, are still recognizable, granules appear in their cytoplasm, and these arrange themselves in rows and unite to form slender fibrils, which at first do not extend beyond the limits of the myoblasts in which they have appeared, but later, as the fusion of the cells proceeds, are continued from one cell territory into the other. Fig. 118.—Section through the Heart- wall of a Duck Embryo of Three Days. —(M. Heidenhain.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appeara
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Keywords: ., bookautho, bookcentury1900, bookdecade1910, booksubjectembryology
