Striated muscle myocyte

 

  

Sarcomere is the muscle cell. It is the muscle fiber. The cytoplasm is called the sarcoplasm.   It is disposed in a syncytial fashion and multinucleated.   It is cylindrical or prismatic in shape.   It has various types of organelles inside the sarcoplasm.   There occurs a special type of endoplasmic reticulum (called sarcoplasmic reticulum) vacuolar system responsible for intra and extra cellular transportation of materials.   It has been recently demonstrated that the sarcoplasmic reticulum becomes active during excitation of the muscle cells which is the process prior to contraction.   It has also been said that the sarcoplasmic reticulum is responsible for the transportation of Ca2+ and the propagation of impulses from the sarcolemma right into the interior of the muscle fiber to reach the contractile elements inside the muscle cell.   This is the phenomenon of excitation-contraction coupling.

The sarcoplasmic reticulum intimately surrounds the myofibrils and form centrotubules which are part of the so called T system of membranes in the sarcoplasmic reticulum. There are numerous mitochondria in muscle cells.   They are called sarcosomes.   They are of various shapes and sizes and are involved in cellular respiration within the muscle cell.   There are some Golgi apparatus, special granules and myofibrils.   Myofibrils are responsible for the contraction of the muscles.   They are the contractile elements.   They are also responsible for the striations seen in the muscle cell.   Under the electron microscope the myofibrils have been resolved to have myofilaments of two nature- myosin and actin. Myosin is thee thick and short myofilament.   It has also been demonstrated that it has ATPase (adenosine triphosphatase) activities

 
         

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   Smooth muscle

   Striated muscle

   Cardiac muscle

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Creator: Oluwole Ogunranti

 

 
    

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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