File:Keith1902 fig042.jpg - Revision history

Z8600021 at 07:13, 18 Mayıs 2015

2015-05-18T07:13:07Z

← Older revision		Revision as of 18:13, 18 Mayıs 2015
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	==Fig. 42 A transverse section showing how the Walls of the Antrum are formed==		==Fig. 42 A transverse section showing how the Walls of the Antrum are formed==

	The antrum of the mastoid represents the extreme outer or posterior end of the first cleft recess (~~Figs~~. 39 and 40). It is formed at the same time and in the same manner as the tympanum. Its use is unknown, but it has frequently to be exposed by the surgeon to remove the effects of chronic middle ear disease. At birth its outer wall is formed by the thin post-auditory part of the squamosal (~~Figs~~. 41 and 42). The squamosal forming its outer wall is then only 2 mm. thick, but every year until the 20 th, or later, this plate increases nearly 1 mm. in thickness, so that by the 20th year the antrum is buried by a plate of bone about 20 mm. thick. There is a great individual variation, however, in the thickness of its outer wall. The antrum lies above and behind the level of the external auditory meatus ; the post-auditory spine and suprameatal triangle formed by the post-auditory part of the squamosal lie over it and serve as surface guides to it. The antrum opens in front into the attic of the tympanum. The tegmen tympani (Fig. 42) forms its roof and the petro-mastoid its floor and inner wall. The aqueductus Fallopii runs down the inner wall of its mouth (Fig. 43), and in its inner wall is situate the external semicircular canal. The petro-squamous suture in its roof (Fig. 42), and the masto-squamous suture on its outer wall (Fig. 14 B), become closed in the second year, and thus the escape of pus from it is rendered more difficult.		The antrum of the mastoid represents the extreme outer or posterior end of the first cleft recess ([[:File:Keith1902 fig039.jpg\|Fig. 39]] and [[:File:Keith1902 fig040.jpg\|Fig. 40]]). It is formed at the same time and in the same manner as the tympanum. Its use is unknown, but it has frequently to be exposed by the surgeon to remove the effects of chronic middle ear disease. At birth its outer wall is formed by the thin post-auditory part of the squamosal ([[:File:Keith1902 fig041.jpg\|Fig. 41]] and [[:File:Keith1902 fig042.jpg\|Fig. 42]]). The squamosal forming its outer wall is then only 2 mm. thick, but every year until the 20 th, or later, this plate increases nearly 1 mm. in thickness, so that by the 20th year the antrum is buried by a plate of bone about 20 mm. thick.


			There is a great individual variation, however, in the thickness of its outer wall. The antrum lies above and behind the level of the external auditory meatus ; the post-auditory spine and suprameatal triangle formed by the post-auditory part of the squamosal lie over it and serve as surface guides to it. The antrum opens in front into the attic of the tympanum. The tegmen tympani ([[:File:Keith1902 fig042.jpg\|Fig. 42]]) forms its roof and the petro-mastoid its floor and inner wall. The aqueductus Fallopii runs down the inner wall of its mouth ([[:File:Keith1902 fig043.jpg\|Fig. 43]]), and in its inner wall is situate the external semicircular canal. The petro-squamous suture in its roof ([[:File:Keith1902 fig042.jpg\|Fig. 42]]), and the masto-squamous suture on its outer wall (Fig. 14 B), become closed in the second year, and thus the escape of pus from it is rendered more difficult.

Z8600021 at 00:11, 21 Ocak 2014

2014-01-21T00:11:58Z

← Older revision		Revision as of 11:11, 21 Ocak 2014
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	==Fig. 42 A transverse section showing how the Walls of the Antrum are formed==		==Fig. 42 A transverse section showing how the Walls of the Antrum are formed==

			The antrum of the mastoid represents the extreme outer or posterior end of the first cleft recess (Figs. 39 and 40). It is formed at the same time and in the same manner as the tympanum. Its use is unknown, but it has frequently to be exposed by the surgeon to remove the effects of chronic middle ear disease. At birth its outer wall is formed by the thin post-auditory part of the squamosal (Figs. 41 and 42). The squamosal forming its outer wall is then only 2 mm. thick, but every year until the 20 th, or later, this plate increases nearly 1 mm. in thickness, so that by the 20th year the antrum is buried by a plate of bone about 20 mm. thick. There is a great individual variation, however, in the thickness of its outer wall. The antrum lies above and behind the level of the external auditory meatus ; the post-auditory spine and suprameatal triangle formed by the post-auditory part of the squamosal lie over it and serve as surface guides to it. The antrum opens in front into the attic of the tympanum. The tegmen tympani (Fig. 42) forms its roof and the petro-mastoid its floor and inner wall. The aqueductus Fallopii runs down the inner wall of its mouth (Fig. 43), and in its inner wall is situate the external semicircular canal. The petro-squamous suture in its roof (Fig. 42), and the masto-squamous suture on its outer wall (Fig. 14 B), become closed in the second year, and thus the escape of pus from it is rendered more difficult.


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Z8600021: ==Fig. 42 A transverse section showing how the Walls of the Antrum are formed== {{Keith1902_4_figures}} {{Human embryology morphology 1902 footer}}

2013-12-29T16:40:52Z

==Fig. 42 A transverse section showing how the Walls of the Antrum are formed== {{Keith1902_4_figures}} {{Human embryology morphology 1902 footer}}

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==Fig. 42 A transverse section showing how the Walls of the Antrum are formed==

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