| musculus iliocostalis dorsi | <anatomy, muscle> Origin, medial side of angles of lower six ribs; insertion, angles of upper six ribs; action, extends, abducts, and rotates thoracic vertebrae; nerve supply, dorsal branches of thoracic nerves. Synonym: musculus iliocostalis thoracis, musculus iliocostalis dorsi. (05 Mar 2000) |
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| musculus iliocostalis lumborum | <anatomy, muscle> Origin, with erector spinae; insertion, the angles of lower six ribs; action, extends, abducts, and rotates lumbar vertebrae; nerve supply, dorsal branches of thoracic and lumbar nerves. Synonym: musculus iliocostalis lumborum, lumbar iliocostal muscle, musculus sacrolumbalis. (05 Mar 2000) |
| musculus iliocostalis thoracis | <anatomy, muscle> Origin, medial side of angles of lower six ribs; insertion, angles of upper six ribs; action, extends, abducts, and rotates thoracic vertebrae; nerve supply, dorsal branches of thoracic nerves. Synonym: musculus iliocostalis thoracis, musculus iliocostalis dorsi. (05 Mar 2000) |
| musculus iliopsoas | <anatomy> A compound muscle, consisting of the iliacus musculus and psoas major musculus. Origin, The transverse processes of L1-L5; insertion, lesser trochanter of the femur; action, flexes the thigh, laterally rotates and adducts thigh. Synonym: musculus iliopsoas. (05 Mar 2000) |
| musculus incisivus labii inferioris | Inferior incisive bundle of origin of orbicularis oris musculus. (05 Mar 2000) |
| musculus incisivus labii superioris | Superior incisive bundle of origin of orbicularis oris musculus. (05 Mar 2000) |
| musculus incisurae helicis | An occasional muscle on the cranial surface of the auricle spanning the antitragohelicine fissure. Synonym: musculus incisurae helicis, musculus intertragicus. (05 Mar 2000) |
| musculus infracostalis | <anatomy> One of a number of inconstant muscles of the posterolateral thoracic wall having the same direction as the internal intercostal muscles but extending across (deep to) one or more ribs. Synonym: musculus subcostalis, musculus infracostalis. (05 Mar 2000) |
| musculus infraspinatus | <anatomy, muscle> Origin, infraspinous fossa of scapula; insertion, middle facet of greater tubercle of humerus; action, extends arm and rotates it laterally; nerve supply, suprascapular (from fifth to sixth cervical spinal nerves). Synonym: musculus infraspinatus. (05 Mar 2000) |
| musculus intercostales externi | Each arises from lower border of one rib and pass obliquely downward and forward to be inserted into the upper border of rib below; action, contract during inspiration, also maintain tension in the intercostal spaces to resist mediolateral movement; nerve supply, intercostal. Synonym: musculus intercostales externi. (05 Mar 2000) |
| musculus interosseus palmaris | <anatomy> Three muscles in the hand; origin, first: ulnar side of second metacarpal; second and third: radial sides of fourth and fifth metacarpals; insertion, first: into ulnar side of index; second and third: into radial sides of ring and little fingers; action, adducts fingers toward axis of middle finger; nerve supply, ulnar. See: flexor pollicis brevis muscle. Synonym: musculus interosseus palmaris, musculus interosseus volaris. (05 Mar 2000) |
| musculus interosseus plantaris | <anatomy> Three intrinsic muscles of foot; origin, the medial side of the third, fourth, and fifth metatarsal bones; insertion, corresponding side of proximal phalanx of the same toes; action, adducts three lateral toes; nerve supply, lateral plantar. Synonym: musculus interosseus plantaris. (05 Mar 2000) |
| musculus interosseus volaris | <anatomy> Three muscles in the hand; origin, first: ulnar side of second metacarpal; second and third: radial sides of fourth and fifth metacarpals; insertion, first: into ulnar side of index; second and third: into radial sides of ring and little fingers; action, adducts fingers toward axis of middle finger; nerve supply, ulnar. See: flexor pollicis brevis muscle. Synonym: musculus interosseus palmaris, musculus interosseus volaris. (05 Mar 2000) |
| musculus interspinalis cervicis | Origin, tubercle of spinous process of cervical vertebra; insertion, tubercle of spinous process of next superior vertebra; action, extends the neck; nerve supply, dorsal rami of cervical nerves. Synonym: musculus interspinalis cervicis, cervical interspinal muscle. (05 Mar 2000) |
| musculus interspinalis lumborum | Origin, superior margin of lumbar spinous process; insertion, inferior margin of next superior spinous process; action, extends lumbar vertebrae; nerve supply, dorsal primary rami of lumbar spinal nerves. Synonym: musculus interspinalis lumborum, lumbar interspinal muscle. (05 Mar 2000) |