Smooth muscle

A smooth muscle fiber, such as this in the wall of an arteriole, is a spindle-shaped cell with a centrally located nucleus.  Prominent dense bodies serve as attachment points for actin myofilaments and are visible in the sarcoplasm of these cells, as well as beneath the sarcolemma.  Myosin myofilaments are intercalated within the actin bundles.  4000x

A smooth muscle fiber, such as this in the wall of an arteriole, is a spindle-shaped cell with a centrally located nucleus.  Prominent dense bodies serve as attachment points for actin myofilaments and are visible in the sarcoplasm of these cells, as well as beneath the sarcolemma.  Myosin myofilaments are intercalated within the actin bundles.  4000x

A smooth muscle fiber, such as this in the wall of an arteriole, is a spindle-shaped cell with a centrally located nucleus.  Prominent dense bodies serve as attachment points for actin myofilaments and are visible in the sarcoplasm of these cells, as well as beneath the sarcolemma.  Myosin myofilaments are intercalated within the actin bundles.  4000x

Like skeletal muscle, smooth muscle fibers produce an external lamina, which is surrounded by reticular fibers.  Both structures aid in transmitting the force of muscle contraction.

The cytoplasm of smooth muscle fibers is filled with interlacing, overlapping myofilaments.  Unlike striated muscles, these filaments are not organized into myofibrils.  Myosin filaments are scattered throughout the sarcoplasm.  Actin myofilaments are anchored in alpha-actinin containing dense bodies located in the cytoplasm and beneath the plasma membrane.

The cytoplasm of smooth muscle fibers is filled with interlacing, overlapping myofilaments.  Unlike striated muscles, these filaments are not organized into myofibrils.  Myosin filaments are scattered throughout the sarcoplasm.  Actin myofilaments are anchored in alpha-actinin containing dense bodies located in the cytoplasm and beneath the plasma membrane.