| dorsal interosseous muscles of foot | Four muscles in the foot; origin, from sides of adjacent metatarsal bones; insertion, first into medial, second into lateral side of proximal phalanx of second toe, third and fourth into lateral side of proximal phalanx of third and fourth toes; action, abduct toes 2-4 from an axis through the second toe; nerve supply, lateral plantar. Synonym: musculi interossei dorsalis pedis. (05 Mar 2000) |
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| dorsal interosseous muscles of hand | Four muscles in the hand; origin, sides of adjacent metacarpal bones; insertion, proximal phalanges and extensor expansion, first on radial side of index, second on radial side of middle finger, third on ulnar side of middle finger, fourth on ulnar side of ring finger; action, abduct fingers 2-4 from the axis of the middle finger, nerve supply, ulnar. Synonym: musculi interossei dorsalis manus. (05 Mar 2000) |
| dorsal muscles | The muscles of the back in general, including those attaching the shoulder girdle to the trunk posteriorly, the posterior serratus muscles, and the erector spinae. Synonym: musculi dorsi, dorsal muscles. (05 Mar 2000) |
| inferior retinaculum of extensor muscles | A Y-shaped ligament restraining the extensor tendons of the foot distal to the ankle joint. Synonym: retinaculum musculorum extensorum inferius, cruciate ligament of leg, inferior retinaculum of extensor muscles, ligamentum cruciatum cruris. (05 Mar 2000) |
| infrahyoid muscles | The small, flat muscles inferior to the hyoid bone including the sternohyoid, omohyoid, sternothyroid, thyrohyoid, and levator muscle of the thyroid gland. Synonym: musculi infrahyoidei, strap muscles. (05 Mar 2000) |
| intercostal muscles | Respiratory muscles that arise from the lower border of one rib and insert into the upper border of the adjoining rib, and contract during inspiration or respiration. (12 Dec 1998) |
| intermediate layer of the transversospinalis muscles | <anatomy, muscle> Origin, from the sacrum, sacroiliac ligament, mamillary processes of the lumbar vertebrae, transverse processes of thoracic vertebrae, and articular processes of last four cervical vertebrae; insertion, into the spinous processes of all the vertebrae up to and including the axis; action, rotates vertebral column; nerve supply, dorsal primary rami of spinal nerves. Synonym: musculus multifidus, intermediate layer of the transversospinalis muscles, musculus multifidus spinae. (05 Mar 2000) |
| interosseous muscles | Muscles which arise from and run between the long (metacarpal and metatarsal) bones of the hand and foot, extending to and producing movement of the digits. See: dorsal interosseous muscles of foot, dorsal interosseous muscles of hand, palmar interosseous muscle, plantar interosseous muscle. Synonym: musculi interossei. (05 Mar 2000) |
| interspinales muscles | The paired muscles between spinous processes of adjacent vertebrae; subdivided into cervical, thoracic, and lumbar muscles. Synonym: musculi interspinales, interspinal muscles. (05 Mar 2000) |
| interspinal muscles | The paired muscles between spinous processes of adjacent vertebrae; subdivided into cervical, thoracic, and lumbar muscles. Synonym: musculi interspinales, interspinal muscles. (05 Mar 2000) |
| intertransversarii muscles | The paired muscles between transverse processes of adjacent vertebrae; there are anterior and posterior muscles in the cervical region; lateral and medial muscles in the lumbar region; and single muscles in the thoracic region. Synonym: musculi intertransversarii, intertransverse muscles. (05 Mar 2000) |
| intertransverse muscles | The paired muscles between transverse processes of adjacent vertebrae; there are anterior and posterior muscles in the cervical region; lateral and medial muscles in the lumbar region; and single muscles in the thoracic region. Synonym: musculi intertransversarii, intertransverse muscles. (05 Mar 2000) |
| intrinsic muscles | Muscles fully contained (origin, belly, and insertion) within the structure under consideration. For example, the interossei and lumbrical muscles are intrinsic muscles of the hand. (05 Mar 2000) |
| intrinsic muscles of foot | Muscles fully contained (origin, belly, insertion) in the foot and toes. These muscles are arranged in four layers and all are innervated by the plantar branches of the tibial nerve. Although they may be capable of producing the actions described under their individual entries, as a group the primary function of the intrinsic muscles of the foot is to provide dynamic support of the longitudinal arch of the foot, resisting the forces which act momentarily to spread the arch during walking and running. (05 Mar 2000) |
| involuntary muscles | Muscle's not ordinarily under control of the will; except in the case of the heart, they are smooth (nonstriated) muscle's, innervated by the autonomic nervous system. (05 Mar 2000) |