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Plate 6. Otic Capsule - Lateral and Medial Aspect

In the otic capsule (figs. 6 and 7) we may distinguish a larger dorsolateral portion, which contains the semicircular canals, and which may therefore be known as the pars canalicularis (Voit), and a smaller, ventro-median portion, which contains the cochlear part of the membranous labyrinth, and which may therefore be termed the pars cochlearis. Voit has restricted the use of the term 'pars vestibularis' to the dorsal part of the pars cochlearis, which presents the fenestrae vestibuli and perilymphatica and the fenestrae for the vestibular division of the eighth cranial nerve. It contains the first, or unwound, portion of the ductus cochlearis. I shall adopt this usage of the term in this description.

The medial surface (fig. 7) is more extensive than the lateral. Its cranial and dorsal borders are the same as those of the lateral surface; its ventral border is marked above by a rounded ridge passing downwards from the superior utriculoampullary prominence to the superior otic notch, and below by the posterior semicircular prominence, which, as has been seen, terminates ventro-medially in the inferior utriculoampullary prominence, the latter bearing a ventrally-projecting process, the processus interperilymphatica (Voit). The middle portion of the ventral boundary is formed by the transition of the medial surface of the pars canalicularis into that of the vestibular portion of the pars cochlearis. As has been mentioned the medial surface is convex, and presents in its central area as its most prominent object the prominentia cruris communis (Voit), formed by the crus conmiune within (fig. 9). Upon the dorsal part of this prominence is seen the long, almost horizontal, slit-like foramen endolymphaticum, for the outlet of the ductus endolymphaticus. Both lips of this foramen are formed of a young type of cartilage and it may be noted that the upper lip projects medially in its dorsal part to ovei^hq-ng the duct, and is continued dorsally past the foramen to form a groove, in which the duct lies (fig. 7). The dorsal extremity of this upper lip appears as a short, free process, overlying the duct.


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Links: plate 1 | plate 2 | plate 3 | plate 4 | plate 5 | plate 6 | fig 6 | fig 7 | plate 7 | fig 8 | fig 9 | plate 8 | fig 10 | plate 9 | fig 11 | fig 12 | plate 10 | plate 11 | fig 14 | Macklin 1914 part 1 | Macklin 1914 part 2 | Skull Development


Reference

Macklin CC. The skull of a human fetus of 40 mm 1. (1914) Amer. J Anat. 16(3): 317-386.



Cite this page: Hill, M.A. (2024, June 15) Embryology Macklin1914 plate06.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Macklin1914_plate06.jpg

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