What's the difference between ommatidium and rhabdom?
Ommatidium
Definition:
(n.) One of the single eyes forming the compound eyes of crustaceans, insects, and other invertebrates.
Example Sentences:
(1) Nine cell axons arising from each ommatidium leave the retina.
(2) All retinula cells run the entire length from the cone to the basal lamina, although two, called the proximal cells, only contribute to the lowest third of the rhabdom, and one of either cell 6 or cell 7 on our arbitrary numbering system forms its axon one third the way up the ommatidium.
(3) An admittance function was defined as the percentage of the rays reaching the rhabdom with respect to those entering the ommatidium.
(4) These results suggest that almost the whole area of the compound eye may contain circadian photoreceptors, and that the photic information from each ommatidium may additively affect the circadian clock to entrain via neural integration mechanisms.
(5) Each visual unit (ommatidium) of the compound eye of the honey bee contains nine retinula cells, six of which end as axons in the first synaptic ganglion, the lamina, and three in the second optic ganglion, the medulla.
(6) A technique allowing light- and electron microscopy to be performed on the same silver-impregnated sections has made it possible to follow all types of retinula axons of one ommatidium to their terminals in order to study the shape of the terminal branches with their position in the cartridge.
(7) sevenless protein is present transiently at high levels in at least 9 cells in each developing ommatidium and is detectable several hours before any overt differentiation of R7.
(8) The dioptric elements in each ommatidium consist of a laminar cornea, which is flat externally and convex internally, and a bipartite crystalline cone.
(9) In the fully differentiated ommatidium only two types of junction remain, these are: desmosomes and rhabdomeric junctions.
(10) The development of the R7 photoreceptor cell, one of the eight photoreceptor cells in the ommatidium, is best understood.
(11) 1) One ommatidium in the compound eye is the functional unit in image perception but contains in its component retinular cells subunits which can work independently in detecting other visual parameters, such as polarization.
(12) A pattern is described where eight axons from three adjacent ommatidia join in one cartridge; and conversely, the axons from one ommatidium split and join to three cartridges.
(13) At least one, probably two, retinula fibres per ommatidium penetrate this layer to end in the medulla, via the first optic chiasma.
(14) The junction between lens and LPC's has critical structural value in that (1) this is the sole anchorage to the lens by the lengthy remainder of the ommatidium, and (2) LPC's enclose the semiliquid pseudocone in the most distal portion of the pseudocone.
(15) The effectiveness of lateral inhibition, measured as spike response decrement in a test ommatidium, produced by activity in a group of neighboring ommatidia, decreases as temperature decreases (Q(10) of 2.6).
(16) Moreover, experimental observations indicate that for intact undamaged retinae in intense spatially uniform illumination, the total inhibitory influence at a given ommatidium can exceed the excitation of that ommatidium.
(17) Pigment cells envelop the entire ommatidium, and pigment granules also are abundant throughout the cytoplasm of the 8 retinular cells.
(18) The rhabdom occupies the basal thirty percent of the ommatidium and can be divided into nine segments of parallel microvilli.
(19) In each ommatidium, cells that are sensitive to the same orientation of the electric-vector of polarized light are coupled electrically.
(20) Each ommatidium is surrounded by pigment cells, and pigment granules also appear throughout the cytoplasm of the retinular cells.
Rhabdom
Definition:
(n.) One of numerous minute rodlike structures formed of two or more cells situated behind the retinulae in the compound eyes of insects, etc. See Illust. under Ommatidium.
Example Sentences:
(1) On dark-adaptation of the 11-day adult eye, the rhabdomers move towards the cuticle.
(2) The rhabdom of the larval eye, if cut longitudinally, exhibits a "banded" structure over its entire length; in the adult the banded part is confined to the distal end, and the rhabdom is tiered.
(3) In all other ommatidia, the proximal parts of the rhabdoms show radially arranged microvilli, whereas the distal parts may reveal different patterns, frequently with microvilli in two directions or sometimes even in one direction.
(4) A calculation of the theoretical field size of individual retinula cells from measurments of refractive index and lens dimensions predicts that cells which participate in the central rhabdom will have acceptance angles near 3 degrees.
(5) All retinula cells run the entire length from the cone to the basal lamina, although two, called the proximal cells, only contribute to the lowest third of the rhabdom, and one of either cell 6 or cell 7 on our arbitrary numbering system forms its axon one third the way up the ommatidium.
(6) In the dark, a distinct gradient of activity was observed with radioactivity concentrated distally and declining toward the proximal end of the rhabdome.
(7) An admittance function was defined as the percentage of the rays reaching the rhabdom with respect to those entering the ommatidium.
(8) In spite of a one h exposure to light, rhabdom microvilli show no disintegration or disruption of membranes.
(9) The rhabdom of isolated small photoreceptors is surrounded by a calyx originating from the soma, so that it appears to be located internally.
(10) After 1-h illumination (225-320 lux), further reduction of rhabdom diameter was modest in control retinae but precipitate in those treated with OKA.
(11) Foot cells which lie immediately below the rhabdom also contain similar junctions and actin is tentatively identified in these cells.
(12) Three different fractions of visual cell fragments were prepared from the retina: the MV-fraction containing the rhabdomal microvilli, and the PVH- and PVL-fractions containing the photic vesicles located in the visual cell body.
(13) Sometimes seven and sometimes eight retinular cells closely appose the proximal tip of the cone and bear the microvilli of the rhabdom.
(14) Rhabdom sizes were not compromised by OKA, nor by either of the two protein kinase activators, SC-9 or PDA when each was deployed alone in darkness.
(15) A clear zone between dioptric structures and the rhabdom layer is absent.
(16) In Loricera and Agonum roots at the level of the proximal rhabdom are not continuous with the rootlets or short roots associated with the centrioles.
(17) In both cases, microvilli of the rhabdom were severely disrupted and the retinular cytoplasm contained numerous multivesicular bodies.
(18) Exposure to light seems to activate a transport mechanism that results in the redistribution of retinoid between the inner segments and rhabdomes and chromophore exchange among the photopigments.
(19) Quantification of the electron microscopic autoradiograms revealed that labeling of the cytoplasm was greater than the rhabdome at 2, 5, and 30 minutes and reached a peak at 12 hours.
(20) Extensive areas of gap junctions which occur between the rhabdoms and the membranes of large and small cells suggest that the cells may be electrically coupled to one another.