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Structure and Functions of Muscles

Types, Locations and Function of Muscles

  • There are three types of muscles, located at various parts of the body.
  • In order to function all use energy in form of ATP.
  • These include smooth, skeletal and cardiac muscles.


Smooth Muscle (Involuntary Muscles)

  • These are spindle-shaped and contain filaments with myofibrils.
  • Each muscle is bound by plasma membrane.
  • They are found lining internal organs such as alimentary canal, bladder, and blood vessels.
  • They are controlled by involuntary part of the nervous system.
  • They are concerned with movement of materials along the organs and tubes.
  • They contract slowly and fatigue slowly .

Skeletal Muscle (striated or voluntary muscle)

  • Skeletal muscles are striated and have several nuclei.
  • They are long fibres each containing myofibrils and many mitochondria.
  • They have cross-striations or stripes.
  • They are also called voluntary muscles because the contraction is controlled by voluntary nervous system.
  • They are surrounded by connective tissue and are attached to bones by tendons.
  • Their contraction brings about movement of bone, resulting in locomotion.
  • They contract quickly and fatigue quickly.

               skeletal muscle      ggg


Cardiac Muscle

  • Consist of a network of striated muscle fibres connected by bridges.
  • Are short cells with numerous mitochondria and uninucleate.
  • They are found exclusively in the heart.
  • Contractions of cardiac muscles are generated from within the muscles and are rhythmic and continuous hence they are myogenic.
  • They do not tire or fatigue.
  • The rate can be modified by involuntary nervous system.
  • Their contractions result in the heart pumping blood.


Role of muscles in movement of the human arm

  • Muscles that bring about movement are antagonistic, i.e. when one set contracts the other relaxes.


Antagonistic muscles of human forelimb

  • The biceps muscles of the forelimb act as flexors while the triceps muscles act as extensors.
  • The biceps has its point of origin on the scapula and the point of insertion on the radius.
  • The triceps has its points of origin on the scapula and humerus and is inserted on the ulna.
  • When the muscles contract, the limb acts as a lever with the pivot at the joint.
  • Contraction of biceps muscles bends (flexes) the arm while contractions of triceps extends the arm.