| mactra | <zoology> Any marine bivalve shell of the genus Mactra, and allied genera. Many species are known. Some of them are used as food, as Mactra stultorum, of Europe. See Surf clam, under Surf. Origin: NL, fr. Gr. Kneading trough, fr. To knead. Source: Websters Dictionary (01 Mar 1998) |
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| macula | 1. <dermatology> A stain, spot or thickening. 2. <ophthalmology> Often used alone to refer to the macula retinae. (10 Jan 1998) |
| macula adherens | Spot desmosome: see desmosome. (18 Nov 1997) |
| macula albida | Gray-white or white, rounded or irregularly shaped, slightly opaque patches or spots that are sometimes observed postmortem in the epicardium, especially in middle-aged or older persons; they result from fibrous thickening, and sometimes hyalinization, of the epicardium; similar lesions may also occur in the visceral layer of the peritoneum. Synonym: macula lactea, macula tendinea, tache blanche, tache laiteuse, tendinous spot, white spot. (05 Mar 2000) |
| macula atrophica | An atrophic glistening white spot on the skin. (05 Mar 2000) |
| macula cerulea | A bluish stain on the skin caused by the bites of fleas or lice, especially pediculosis pubis. Synonym: blue spot, tache bleuatre. (05 Mar 2000) |
| macula communicans | <cell biology> A junction between two cells consisting of many pores that allow the passage of molecules up to about 900D. Each pore is formed by an hexagonal array (connexon) of six transmembrane proteins (connexins) in each plasma membrane: when mated together the pores open, allowing communication and the interchange of metabolites between cells. Electrical synapses are gap junctions and metabolic cooperation depends upon the formation of gap junctions. (18 Nov 1997) |
| macula communis | The thickened area in the medial wall of the auditory vesicle that later subdivides to form the maculae of the sacculus and utriculus as well as the cristae of the ampullae of the saemicircular ducts. (05 Mar 2000) |
| macula corneae | A moderately dense opacity of the cornea. Synonym: corneal spot. (05 Mar 2000) |
| macula cribrosa | One of three areas on the wall of the vestibule of the labyrinth, marked by numerous foramina giving passage to nerve filaments supplying portions of the membranous labyrinth, macula cribrosa inferior, located in the posterior bony ampulla for passage of posterior ampullary nerve fibres, macula cribrosa media, area near the base of the cochlea through which the saccular nerve fibres pass, macula cribrosa superior, perforated area above the elliptical recess for passage of the utriculoampullary nerve fibres, macula cribrosa quarta, a name sometimes applied to the opening for the cochlear nerve. (05 Mar 2000) |
| macula densa | A closely packed group of densely staining cells in the distal tubular epithelium of a nephron, in direct apposition to the juxtaglomerular cells; they may function as either chemoreceptors or as baroreceptors feeding information to the juxtaglomerular cells. (05 Mar 2000) |
| macula flava | A yellowish spot at the anterior extremity of the rima glottidis where the two vocal folds join. (05 Mar 2000) |
| macula germinativa | Archaic term for the nucleolus in the nucleus of an ovum; also refers to any germinal area. (05 Mar 2000) |
| macula gonorrhoica | A spot of red brighter than the surrounding membrane, at the congested orifice of the duct of Bartholin's gland, sometimes seen in gonorrhoea. Synonym: Saenger's macula. (05 Mar 2000) |
| macula lactea | Gray-white or white, rounded or irregularly shaped, slightly opaque patches or spots that are sometimes observed postmortem in the epicardium, especially in middle-aged or older persons; they result from fibrous thickening, and sometimes hyalinization, of the epicardium; similar lesions may also occur in the visceral layer of the peritoneum. Synonym: macula lactea, macula tendinea, tache blanche, tache laiteuse, tendinous spot, white spot. (05 Mar 2000) |