| obturator membrane | The thin membrane of strong interlacing fibres filling the obturator foramen. Synonym: membrana obturatoria. (05 Mar 2000) |
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| olfactory membrane | That part of the nasal mucosa having olfactory receptor cells and glands of Bowman. (05 Mar 2000) |
| oral membrane | A bilaminar (ectoderm and endoderm) membrane derived from the prochordal plate; after the embryonic head fold has evolved it lies at the caudal limit of the stomodeum. Synonym: oral membrane, oropharyngeal membrane. (05 Mar 2000) |
| oronasal membrane | A thin, transient epithelial sheet separating the primitive nasal cavity from the stomodeum in the seven-week-old human embryo. Synonym: oronasal membrane. (05 Mar 2000) |
| oropharyngeal membrane | A bilaminar (ectoderm and endoderm) membrane derived from the prochordal plate; after the embryonic head fold has evolved it lies at the caudal limit of the stomodeum. Synonym: oral membrane, oropharyngeal membrane. (05 Mar 2000) |
| otolithic membrane | A gelatinous membrane surmounting the acoustic maculae of the saccule and utricle and containing minute calciferous granules, known as otoconia, otoliths, or statoconia. (12 Dec 1998) |
| outer membrane | The larger of the two membranes of a double membrane. (05 Mar 2000) |
| ovular membrane | The membrane enveloping the yolk; specifically, the thickened cell membrane of large-yolked ova. Synonym: ovular membrane, vitelline membrane. Sometimes used to designate the zona pellucida of a mammalian ovum. Synonym: yolk membrane. (05 Mar 2000) |
| oxygenators, membrane | Devices in which blood and oxygen are separated by a semipermeable membrane, generally of teflon or polypropylene, across which gas exchange occurs. The membrane may be arranged as a series of parallel plates or as a number of hollow fibres; in the latter arrangement, the blood may flow inside the fibres, which are surrounded by gas, or the blood may flow outside the fibres and the gas inside the fibres. (12 Dec 1998) |
| tectorial membrane | A gelatinous membrane, attached to the bony spiral lamina, which overlies the hair cells within the cochlea of the inner ear. (12 Dec 1998) |
| tectorial membrane of cochlear duct | A gelatinous membrane that overlies the spiral organ (Corti) in the inner ear. Synonym: membrana tectoria ductus cochlearis, Corti's membrane, tectorium. (05 Mar 2000) |
| tense part of the tympanic membrane | The greater portion of the tympanic membrane which is tense and firm, contrasting with the small triangular flaccid part of tympanic membrane. Synonym: pars tensa membranae tympani, membrana tensa, membrana vibrans. (05 Mar 2000) |
| tensor muscle of tympanic membrane | <anatomy, muscle> Origin, the cartilaginous part of the auditory (eustachian) tube and the walls of its hemi-canal just above the bony portion of the auditory tube; insertion, handle of malleus; action, draws the handle of the malleus medialward tensing the tympanic membrane to protect it from excessive vibration by loud sounds. Nerve supply, branches of trigeminal through the otic ganglion. Synonym: musculus tensor tympani, tensor muscle of tympanic membrane, Toynbee's muscle. (05 Mar 2000) |
| tertiary egg membrane | See: egg membrane. (05 Mar 2000) |
| thyrohyoid membrane | A thin, fibrous, membranous sheet filling the gap between the hyoid bone and the thyroid cartilage. Synonym: membrana thyrohyoidea, membrana hyothyroidea. (05 Mar 2000) |