| orbicularis muscle | <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) |
|---|---|
| orbicularis oculi muscle | <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) |
| orbicularis oculi reflex | Contraction of the orbicularis oculi muscles upon tapping the margin of the orbit, or the bridge or tip of the nose. Synonym: nose-bridge-lid reflex, nose-eye reflex. (05 Mar 2000) |
| 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) |
| orbicularis phenomenon | A constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision. Synonym: Galassi's pupillary phenomenon, Gifford's reflex, lid-closure reaction, orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon. (05 Mar 2000) |
| orbicularis pupillary reflex | A constriction of both pupils when an effort is made to close eyelids forcibly held apart. A variant of the pupil response to near vision. Synonym: Galassi's pupillary phenomenon, Gifford's reflex, lid-closure reaction, orbicularis phenomenon, orbicularis pupillary reflex, Piltz sign, Westphal's pupillary reflex, Westphal-Piltz phenomenon. (05 Mar 2000) |
| orbital part of orbicularis oculi muscle | orbital part of orbicularis oculi muscle |
| zona | Origin: L, a girdle. See Zone. A zone or band; a layer. Zona pellucida. [NL. <biology> A radiately striated membrane situated next the yolk of an ovum, or separated from it by a very delicate membrane only. Source: Websters Dictionary (01 Mar 1998) |
| zona arcuata | The inner third of the basilar membrane of the cochlear duct extending from the tympanic lip of the osseous spiral lamina to the outer pillar cell of the spiral organ (of Corti). Synonym: zona arcuata, zona tecta. (05 Mar 2000) |
| zona ciliaris | The outer, wider zone of the anterior surface of the iris, separated from the pupillary zone by the collarette. Synonym: zona ciliaris. (05 Mar 2000) |
| zona corona | An irregularly disposed collection of visible veins seen in the skin of people usually of or past middle age; it has no specific connection with any deep structure, such as the diaphragm, and no necessary connection with underlying visceral disease. Synonym: zona corona. (05 Mar 2000) |
| zona dermatica | A ridge of thickened skin surrounding the protrusion in spina bifida. (05 Mar 2000) |
| zona epithelioserosa | The membranous ring, within the zona dermatica, surrounding the protrusion in spina bifida. (05 Mar 2000) |
| zona facialis | Herpes zoster involving the face. (05 Mar 2000) |
| zona fasciculata | The wide middle zone of the adrenal cortex. This zone consists of large lipid-laden cells radially arranged in parallel cords. It converts pregnenolone to cortisol by a series of enzymatically regulated steps. A small amount of corticosterone is formed as a by-product of cortisol synthesis. (12 Dec 1998) |