Muscular System

Muscles are specialized contractile tissue that contain proteins known as actin and myosin. These proteins produce muscle contraction by sliding over each other. Muscles can be categorized into three groups depending on how their contractile fibers are arranged:

Skeletal muscles

  • Skeletal muscles have a striated (striped) appearance and attach to bones by dense connective tissue called tendons.

  • These muscles enact voluntary movements.

  • An example of skeletal muscles includes the pectoralis major muscle.

Smooth muscles

  • Smooth muscles are non-striated.

  • They line the walls of internal organs and facilitate the function of organs.

  • These muscles enable involuntary contractions.

  • An example of smooth muscles is the lining of the gastrointestinal tract.

Cardiac muscles

  • Cardiac muscles have a striated appearance and can be found lining the walls of the heart.

  • These muscles enact involuntary contractions of the walls of the heart.

  • The heart is the only organ that is composed of cardiac muscles.