The ultrastructure of mammalian cardiac muscle

Richard J. Stenger, David Spiro

Research output: Contribution to journalArticlepeer-review

45 Scopus citations


Papillary muscles of rat and dog hearts were fixed in such a way as to prevent excessive shortening during the procedure. The material was embedded in either araldite or methacrylatc and was stained in various ways. The filamentous fine structure of mammalian cardiac muscle is similar to that previously described for striated skeletal muscle. The sarcomeres are composed of a set of thick and thin filaments which interdigitate in the A band proper. The filament ratios and the filamentous array are in accord with those found in skeletal muscle. The functional significance of this twofold array of filaments is not entirely clear. Various other structural aspects of cardiac cells such as surface membranes, mitochondria, nuclei, and cytoplasmic granules are described. The sarcoplasmic reticulum is discussed in detail as are the various structural components forming the intercalated discs. Fairly frequent deep invaginations of the sarcolemma with basement membrane are observed in addition to the intercalated discs. These surface membrane invaginations probably explain the branching appearance of cardiac fibers as seen under the light microscope.

Original languageEnglish
Pages (from-to)325-352
Number of pages28
JournalJournal of Cell Biology
Issue number2
StatePublished - 1 Feb 1961
Externally publishedYes


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