File:Cardiac muscle EM04.jpg

Cardiac Muscle Electron Micrograph

This is a historic (1969) EM showing key features in cardiac muscle ultrastructure. (Stain - Osmium)

Fig 4 Electron micrograph of somewhat more than one sarcomere length of papil- lary muscle fixed at the optimum point on the length-tension curve . The sarcomere length is -2.3y.The thin actin filaments can be seen in the I bands, and both thick and thin fila- ments are discernible in the A band. The prominent M line (M) shows a faint striation with a period of 200 A. The narrow pale regions on either side of the M line demarcate the pseudo H zone (Ps II).At this sarcomere length the tips of the actin filaments are very near the margins of the pseudo H zone. Therefore no true H zone can be seen. X 53,000.

Fig 5 A micrograph of a similar segment from a papillary muscle stretched beyond the optimum length for development of tension . The sarcomere length is noticeably greater (2.6 μ) than in Fig.4, but the length of the A band remains constant . In stretching, the ends of the thin filaments have been pulled away from the M line so that a true H zone (II) is discernible. X 53,000.

Legend

• Nel - nucleus.
• Mt - Rows of mitochondria appear to divide the contractile substance into myofibril-like units but, unlike the true myofibrils of skeletal muscle, these branch and rejoin and are quite variable in width.
• Mfl - Myofilaments.
• Cap - Capillary.

Original image X 6,700.

Links: EM Image | EM Image cells labeled | HM Practical - Cardiac Histology

Reference

Fawcett DW & McNutt NS. (1969). The ultrastructure of the cat myocardium. I. Ventricular papillary muscle. J. Cell Biol. , 42, 1-45. PMID: 4891913

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Original article figure (FIG. 4 and 5) has been scaled and rotated.

Cite this page: Hill, M.A. (2024, April 26) Embryology Cardiac muscle EM04.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Cardiac_muscle_EM04.jpg

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G