Glossary

Author: Glossary

  • Twitch muscle

    Muscle fibers that can conduct axon potentials along their cell membranes. Almost all skeletal muscle in humans is twitch muscle. A very small number of muscles in humans are tonic muscles.  

  • Tricipital muscle

    A muscle with three tendons of origin and a single, common insertion.  

  • Triangular muscle

    A flat muscle with a broad origin and narrow insertion.  

  • Tonic muscle

    Slowly contracting muscle fibers that cannot propagate an action potential along their cell membranes. Tonic muscles are uncommon in humans and found only in the extraocular eye muscles, stapedius muscle (in the middle ear), and intrafusal fibers of the muscle spindles.  

  • Thyroepiglottic muscle

    A muscle arising on the inner surface of the thyroid cartilage. It extends upward and backward and is inserted on the epiglottis. It depresses the epiglottis.  

  • Thenar muscle

    The abductor or flexor muscle of the thumb.  

  • Teres major muscle

    A muscle of the shoulder originating on the inferior angle of the scapula and inserted in the lesser tubercle of the humerus. It extends, adducts, and medially rotates the arm and is controlled by the lower subscapular nerve.  

  • Supraspinatus muscle

    The uppermost of the rotator cuff muscles. It originates along the supraspinatus fossa of the scapula, attaches to the top (superior facet) of the greater tubercle of the humerus, works with the deltoid to abduct the arm, and holds the head of the humerus in the glenoid fossa. It is innervated by the suprascapular nerve.…

  • Stabilizer muscle

    A muscle that supports a body segment so muscles attached to it can function.  

  • Sphincter muscle of urinary bladder

    The smooth muscle fibers around the origin of the urethra. Contraction of this muscle prevents urination; relaxation permits it.