Final answer:
Cardiac muscles differ from skeletal muscles primarily in that they contain intercalated discs, which allow for coordinated contractions of the heart. While both muscle types share some characteristics, intercalated discs are unique to cardiac muscle. This key feature enables efficient heart function and distinguishes it from skeletal muscle.
Explanation:
Differences Between Cardiac and Skeletal Muscles
Cardiac muscles are unique in several ways that distinguish them from skeletal muscles. The option that specifically identifies a key difference is:
- C. contain intercalated discs
Cardiac muscle cells have intercalated discs, which are specialized connections between the cells that allow for synchronized contractions of the heart. These discs contain gap junctions, which facilitate electrical communication and help coordinate heartbeats. In contrast, skeletal muscles do not have these intercalated discs.
To elaborate on the other options:
- A. are spindle shaped: This describes smooth muscle, not cardiac muscle.
- B. are striated: Both cardiac and skeletal muscles are striated, so this option does not differentiate them.
- D. contain myofibrils: Both cardiac and skeletal muscles contain myofibrils; myofibrils are the contractile fibers found within muscle cells.
- E. utilize aerobic metabolism: While both muscle types can use aerobic metabolism, this characteristic is not exclusive to cardiac muscle.
In summary, the primary distinguishing feature of cardiac muscle cells as compared to skeletal muscle is the presence of intercalated discs.
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