| musculus obliquus auriculae | <anatomy> A thin band of oblique muscular fibres extending from the upper part of the eminence of the concha to the convexity of the helix, running across the groove corresponding to the inferior crus of the anthelix. Synonym: musculus obliquus auriculae, oblique muscle of auricle, Tod's muscle. (05 Mar 2000) |
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| musculus obliquus capitis inferior | <anatomy, muscle> Origin, spinous process of axis; insertion, transverse process of the atlas; action, rotates head; origin, spinous process of axis; insertion, transverse process of the atlas; nerve supply, suboccipital. See: suboccipital muscles. Synonym: musculus obliquus capitis inferior, inferior oblique muscle of head. (05 Mar 2000) |
| musculus obliquus capitis superior | <anatomy, muscle> Origin, transverse process of atlas; insertion, lateral third of inferior nuchal line; action, rotates head; nerve supply, suboccipital. See: suboccipital muscles. Synonym: musculus obliquus capitis superior, superior oblique muscle of head. (05 Mar 2000) |
| musculus obliquus externus abdominis | <anatomy, muscle> Origin, fifth to twelfth ribs; insertion, anterior half of lateral lip of iliac crest, inguinal ligament, and anterior layer of the rectus sheath; action, diminishes capacity of abdomen, draws thorax downward; nerve supply, thoracoabdominal nerves. Synonym: musculus obliquus externus abdominis, abdominal external oblique muscle. (05 Mar 2000) |
| 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) |
| 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 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) |