On morphology and physiology of the aqueduct of cochlea. Experimental and morphological studies of rhesus monkeys. Experimental studies of the origin of perilymph
Neiger, M.
Fortschritte der Hals-Nasen-Ohrenheilkunde 1968: 113-226
1968
ISSN/ISBN: 0301-3286 PMID: 4978651 Document Number: 5567
The monkey's aquaeductus cochleae is an S-shaped tube of about 4-4.5 mm length, leading from the posterior cranial fossa into the scala tympani. Its internal diameter is 21 [J. in its middle being wider at its ends. The general direction of the tube corresponds with the frontal plane going through the porus acusticus externus. In the inside of the skull it begins in a small cavity, lying on the border between the medial and the caudal face of the pyramid, straight above the foramen jugulare. This cavity opens either directly onto the subarachnoidal space or is separated therefrom by dura mater. The tympanie aperture is elose by the bony boundary of the round window, in the angle between the medial wall and the bottom of the scala tympani. It is behind a little bony hill rising from the bottom of the scala tympani. The bony channel is lined by a layer of tense connective tissue leaving the dura mater as a tubed appendix. At first this layer is as thick as the dura mater getting thinner afterwards up to a few laminae at the tympanie aperture. Loose connective tissue is lying in the so created subdural space being in elose relation with the arachnoidal sheath of the glossopharyngeal nerve. It never has a tubelike form but always forms a more or less tight net. Although it can be said in general that the loose connective tissue is denser in the tympanie, half, no definite rules are set for each individual case. The tympanie aperture opening like a trumpet is always elosed by mesenchymal tissue. It is either filled up with arachnoidal tissue forming a distinct boundary-line towards the perilymphatie space or when being empty a membrane composed of one or more layers stretches over the funnel. This membrane can be followed in both cases either on the bone around the funnel or on the tympanie side of the round window's membrane. It forms here, as weil, the boundary-line to the perilymphatic space. The electron mieroscope shows that this boundary-line whieh also forms the endost of the scala tympani is morphologically identical to the barrier membrane, both being composed of cells, an intercellular substance and capillary vessels. The cells consist of a thieker perikaryon containing the cell nueleus and the cell organellae. Thin membranes leave the perikaryon, whieh also hold mitochondria in thieker areas. The cells of one layer are themselves in elose contact as on endothelial cells. As a rule there is an intercellular substance between the layers but also either an optically empty space or a elose contact may exist. The intercellular substance is cotton like and homogeneous after fixation with osmie acid, filamentous and irregular after fixation with glutarie aldehyd and decalcification with EDTA. It contains bundles of fibres; the fibres of whieh present a periodie transversal striation of about 300A and thin elastic fibres. Researches with polarised light confirm the existence of birefringent structures in the barrier membrane.
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