| musculus iliococcygeus | <anatomy> The posterior part of the levator ani arising from the tendinous arch of the levator ani muscle and inserting on the anococcygeal ligament and coccyx. Synonym: musculus iliococcygeus, iliococcygeal muscle. (05 Mar 2000) |
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| musculus iliocostalis | <anatomy> The lateral division of the erector spinae, having three subdivisions: iliocostalis lumborum musculus, iliocostalis thoracis musculus, and iliocostalis cervicis musculus. Synonym: musculus iliocostalis, iliocostal muscle. (05 Mar 2000) |
| musculus iliocostalis cervicis | <anatomy, muscle> Origin, angles of upper six ribs; insertion, transverse processes of middle cervical vertebrae; action, extends, abducts, and rotates cervical vertebrae; nerve supply, dorsal branches of upper thoracic nerves. Synonym: musculus iliocostalis cervicis, cervical iliocostal muscle, cervicalis ascendens, musculus cervicalis ascendens. (05 Mar 2000) |
| 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) |
| 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 intercostalis internus | <anatomy> Each arises from lower border of rib and passes obliquely downward and backward to be inserted into upper border of rib below; action, contract during expiration, also maintain tension in the intercostal spaces to resist mediolateral movement; nerve supply, intercostal. Synonym: musculus intercostalis internus. (05 Mar 2000) |
| musculus intercostalis intimus | <anatomy> A layer parallel to and essentially part of the internal intercostal muscle but separated from it by the intercostal vessels and nerves.internal intercostal muscle for attachment, action and nerve supply. Synonym: musculus intercostalis intimus. (05 Mar 2000) |