. Human embryology and morphology. Embryology, Human; Morphology. 58 HUMAN EMBRYOLOGY AND MORPHOLOGY otocyst, subdivides into the saccule and utricle (Fig. 44). The division occurs at the entrance of the endolymphatic canal, which thus comes to open into both saccule and utricle. The endo- lymphatic canal, which is simply the stalk of the otocyst, is jjjj-ductus endolymphaticus -semcircular canal. primitiue utricle cochlear canal Fig. 45.—The Otocyst in an Embryo of five weeks ; it shows a demarcation into the various parts of the Membranous Labyrinth. enclosed in the petro-mastoid, its extrem
. Human embryology and morphology. Embryology, Human; Morphology. 58 HUMAN EMBRYOLOGY AND MORPHOLOGY otocyst, subdivides into the saccule and utricle (Fig. 44). The division occurs at the entrance of the endolymphatic canal, which thus comes to open into both saccule and utricle. The endo- lymphatic canal, which is simply the stalk of the otocyst, is jjjj-ductus endolymphaticus -semcircular canal. primitiue utricle cochlear canal Fig. 45.—The Otocyst in an Embryo of five weeks ; it shows a demarcation into the various parts of the Membranous Labyrinth. enclosed in the petro-mastoid, its extremity appearing at the hiatus vestibuli, where it ends beneath the dura mater in a dilatation. It appears to be a vestige of the primitive mouth of the otocyst, which opens on the surface of the head in many fishes. Lastly, the scala media or canal of the cochlea (Fig. 44) grows out from the saccule. There is merely a rudiment of the cochlea in fishes and amphibians. In reptiles, birds, and mono- tremes it is a straight canal—the Lagena. Only in mammals is it arranged spirally. In it the organ of Corti is developed. The Petro-mastoid. Origin.—The mesoblast surrounding the membranous labyrinth becomes cartilaginous at the end of the 3rd month of foetal life, forming the periotic capsule (Figs. 35 and 39). The tissue which immediately surrounds the mem- branous labyrinth does not undergo chondrification, but becomes converted into an open meshwork of cells, the intercellular spaces containing perilymph. The lymphatic space thus formed within the petro-mastoid, containing the saccule and utricle, is the vestibule. The scalae tympani and vestibuli of the cochlea are of similar origin. An oval space on the outer wall of the vestibule is not chondrified; it contains the footplate of the stapes- and forms the foramen ovale. The foramen rotundum also remains unchondrified and separates the tympanum from the: scala tympani (Fig. 43).. Please note that these images are extracted from
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectembryol, bookyear1902
