Organ of Corti overview Dr. Jastrow's electron microscopic atlas

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Dr. med.
H. Jastrow

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Organ of Corti overview (guinea pig)
(for unlabelled original image click here, please!)

A = Sulcus spiralis internus (inner cochlear sulcus); B = Labium vestibulare; C = Limbus laminae spiralis; D = inner tunnel;
Ductus cochlearis (cochlear duct, filled with endolymph [145 mmol/L K⁺; 5 mmol/L Na⁺]);
E = space of Nuël; F = outer tunnel; G = basilar membrane (a very thick basal membrane); H = Ligamentum spirale (spiral ligament);
I = Lamina spiralis ossea (bone lamelle of the modiolus [bone in the centre of the cochlea]);
Lv = Lumina vascularia (lumina of blood vessels arterioles or venoles);
Membrana tectoria (tectorial membrane moves and has direct contact to the stereovilli of the hair cells.
For this reason shear forces move the stereovilli in case of tectorial membrane movement caused by endolymph movement);
Membrana vestibuli (Reißner's membrane or Paries vestibularis ductus cochlearis; is composed of a basement membrane
between 2 single layered squamous epithelia; border between Ductus cochlearis and Scala vestibuli);
Os = Pars petrosa ossis temporalis (petrous part of temporal bone); Pt = Pars tecta of the Scala tympani (simple squamous epithelium);
Sc = stereocilia (hardly visible here, located on tip of all hair cells, in contact to the tectorial membrane);
Scala tympani (tympanic duct, filled with perilymphe [5 mmol/L K⁺; 140 mmol/L Na⁺]);
Scala vestibuli (vestibular duct, filled with perilymphe); Stria vascularis (production of the endolymph is located here, ion pumps
for potassium maintain its extremely high concentration in endolymph);
VIII = Ganglion spirale cochleae, the axons of its neurons comprise the cochlear nerve);
Vc = Vasa capillaria (capillaries; note: stria vascularis is the only epithelium that contains capillaries!)
1 = inner hair cells; 2 = outer hair cells; 3 = inner phalangeal cell; 4 = outer phalangeal cell (Deiters cell);
5 = inner pilar cell; 6 = outer pilar cell; 7 = Boettcher cells; 8 = Claudius cells;
9 = epithelial cells of the basilar membrane in Pars pectinata (cubic or columnar monolayer);
10 = inner sulcus cells; 11 = border cells; 12 = Prominentia spiralis (spiral prominence); 13 = Hensen cells.

The organ of Corti (Organum spirale cochleae) is the sensory organ of hearing in man and most animals. Movement of the tympanic membrane (not visible here) causes auditory bone dislocation. Thus the foot plate of stapes (the last auditory bone) moves the membrane covering the oval fenestra which is the entrance to the inner ear. This causes perilymph movement. The latter is conducted via Membrana vestibuli to the endolymph in Ductus cochlearis which now moves the Membrana tectoria. Thereby attached stereovilli of the sensory inner (1) and outer hair cells (2) get dislocated which causes impulse change in leaving nerve fibres that reach the spiral ganglion (VIII). The auditory nerve (Nervus cochlearis; part of brain nerve VIII)originates here and conducts the impulses to the brainstem.

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