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A 3D overview of the muscular system

3 types of muscles are contained within the human body:

  • Smooth
  • Cardiac
  • Skeletal

Smooth muscles are found in the walls of many organs, such as the stomach and in blood vessels. They have a non-striated appearance and contract involuntarily.

Cardiac muscles are found in the walls of the heart. They also contract involuntarily, but have a striated appearance.

Skeletal muscles are attached to, and move, bones. These muscles contract voluntarily and have a striated appearance. Skeletal muscles are sub-categorized into 4 distinct groups, based on the orientation and arrangement of the muscle fibres:

  • Parallel skeletal muscles consist of fibres that are arranged in parallel to the line pulled during contraction. Parallel muscles can be sub-categorized based on their shape, into:
    • Quadrilateral (eg. the pronatur quadratus)
    • Strap-like (eg. the sartorius)
    • Fusiform (eg. the brachioradialis)
  • Convergent muscles contain fibers that have a wide origin, but converge in order to attach to a narrow tendon.
  • Circular skeletal muscles are made up of fibers that are arranged in a circular manner. They are found at points of openings, where contraction leads to a closure of that opening.
  • Pennate skeletal muscles consist of muscle fibres that are attached to the sides of a tendon, in a manner that is similar to a feather. Pennate muscles can be sub-categorized based on their shape into:
    • Unipennate (eg. the flexor policis longus)
    • Bipennate (eg. the rectus femoris)
    • Multipennate (eg. the deltoid)

Explore the minute details of the muscular system in Complete Anatomy with a suite of 3D learning features such as Muscle Motion, Innervation, Origin/Insertion maps and more. Try it for free today.