| musculus obliquus inferior | <anatomy, muscle> Origin, orbital plate of maxilla lateral to the lacrimal groove; insertion, sclera between the superior and lateral recti; action, primary, extorsion; secondary, elevation and abduction; nerve supply, oculomotor (inferior branch). Synonym: musculus obliquus inferior. (05 Mar 2000) |
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| musculus obliquus internus abdominis | <anatomy, muscle> Origin, iliac fascia deep to lateral part of inguinal ligament, anterior half of crest of ilium, and lumbar fascia; insertion, tenth to twelfth ribs and sheath of rectus; some of the fibres from inguinal ligament terminate in the conjoint tendon; action, diminishes capacity of abdomen, flexes lumbar vertebral column (bends thorax forward); nerve supply, lower thoracic. Synonym: musculus obliquus internus abdominis, abdominal internal oblique muscle. (05 Mar 2000) |
| musculus obliquus superior | <anatomy, muscle> Origin, above the medial margin of the optic canal; insertion, by a tendon passing through the trochlea, or pulley, and then reflected backward, downward, and laterally to the sclera between the superior and lateral recti; action, primary, intorsion; secondary, depression and abduction; nerve supply, trochlear nerve. Synonym: musculus obliquus superior. (05 Mar 2000) |
| musculus obturator externus | <anatomy, muscle> Origin, lower half of margin of obturator foramen and adjacent part of external surface of obturator membrane; insertion, trochanteric fossa of greater trochanter; action, rotates thigh laterally; nerve supply, obturator. Synonym: musculus obturator externus, external obturator muscle. (05 Mar 2000) |
| musculus obturator internus | <anatomy, muscle> Origin, pelvic surface of obturator membrane and margin of obturator foramen; insertion, passes out of pelvis through lesser sciatic foramen, in so doing, making a 90 |
| musculus occipitalis | See: occipitofrontalis muscle. (05 Mar 2000) |
| musculus occipitofrontalis | <anatomy> It is a part of musculus epicranius; the occipital belly (occipitalis muscle) arises from the occipital bone and inserts into the galea aponeurotica; the frontal belly (frontalis muscle) arises from the galea and inserts into the skin of the eyebrow and nose; action, to move the scalp; nerve supply, facial. Synonym: musculus occipitofrontalis, occipitofrontal muscle. (05 Mar 2000) |
| musculus omohyoideus | <anatomy> Formed of two bellies attached to intermediate tendon; origin, by inferior belly from upper border of scapula between superior angle and notch; insertion, by superior belly into hyoid bone; action, depresses hyoid; nerve supply, upper cervical spinal nerves through ansa cervicalis. Synonym: musculus omohyoideus, omohyoid. (05 Mar 2000) |
| musculus opponens digiti minimi | <anatomy, muscle> Origin, hamulus of the hamate bone and transverse carpal ligament; insertion, shaft of fifth metacarpal; action, "cups" palm, drawing ulnar side of hand toward centre of palm; nerve supply, ulnar. Synonym: musculus opponens digiti minimi, musculus opponens digiti quinti, musculus opponens minimi digiti, opposer muscle of little finger. (05 Mar 2000) |
| musculus opponens digiti quinti | <anatomy, muscle> Origin, hamulus of the hamate bone and transverse carpal ligament; insertion, shaft of fifth metacarpal; action, "cups" palm, drawing ulnar side of hand toward centre of palm; nerve supply, ulnar. Synonym: musculus opponens digiti minimi, musculus opponens digiti quinti, musculus opponens minimi digiti, opposer muscle of little finger. (05 Mar 2000) |
| musculus opponens minimi digiti | <anatomy, muscle> Origin, hamulus of the hamate bone and transverse carpal ligament; insertion, shaft of fifth metacarpal; action, "cups" palm, drawing ulnar side of hand toward centre of palm; nerve supply, ulnar. Synonym: musculus opponens digiti minimi, musculus opponens digiti quinti, musculus opponens minimi digiti, opposer muscle of little finger. (05 Mar 2000) |
| musculus opponens pollicis | <anatomy, muscle> Origin, ridge of trapezium and flexor retinaculum; insertion, anterior surface of the full length of the shaft of the first metacarpal bone; action, acts at carpometacarpal joint to "cup" palm, enabling one to oppose thumb to other fingers; nerve supply, median. Synonym: musculus opponens pollicis, opposer muscle of thumb. (05 Mar 2000) |
| musculus orbicularis | <anatomy> A sphincter-like sheet of muscle that encircles an orifice such as the mouth or the palpebral fissures. Synonym: musculus orbicularis, orbicular muscle, orbicularis. (05 Mar 2000) |
| musculus orbicularis oculi | <anatomy> Consists of three portions: orbital part, or external portion, which arises from frontal process of maxilla and nasal process of frontal bone, encircles aperture of orbit, and is inserted near origin; palpebral part, or internal portion, which arises from medial palpebral ligament, passes through each eyelid, and is inserted into lateral palpebral raphe; lacrimal part (tensor tarsi muscle, Duverney's or Horner's muscle) arises from posterior lacrimal crest and passes across lacrimal sac to join palpebral portion; action, closes eye, wrinkles forehead vertically; nerve supply, facial. Synonym: musculus orbicularis oculi, musculus orbicularis palpebrarum, orbicular muscle of eye, sphincter oculi. (05 Mar 2000) |
| musculus orbicularis oris | <anatomy, muscle> Origin, by nasolabial band from septum of the nose, by superior incisive bundle from incisor fossa of maxilla, by inferior incisive bundle from lower jaw each side of symphysis; insertion, fibres surround mouth between skin and mucous membrane of lips and cheeks, and are blended with other muscles; action, closes lips; nerve supply, facial. Synonym: musculus orbicularis oris, musculus sphincter oris, orbicular muscle of mouth, sphincter oris. (05 Mar 2000) |