Paper - The Factors Involved in the Excavation of the Cavities in the Cartilaginous Capsule of the Ear in the Human Embryo: Difference between revisions
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fetus has attained a crown-rump length of about 130 mm. The | fetus has attained a crown-rump length of about 130 mm. The | ||
growth from then until the adult condition is reached may be | growth from then until the adult condition is reached may be | ||
judged by comparing the above with the final stage, labelled | judged by comparing the above with the final stage, labelled adult, which is taken from Schonemann’s reconstruction1 and | ||
reproduced here so as to be on the same scale of enlargement as | |||
the younger stages. Since the cartilaginous labyrinth corresponds closely in form to the membranous labyrinth, particularly as regards the canals, one can see from figure 1 that there | |||
is a progressive increase in the size of the cartilaginous chambers | |||
throughout the Whole embryonic period. | |||
'''Fig. 1''' Median views of wax-plate models of the left membranous labyrinth | |||
in human embryos having crown-rump lengths as indicated in the figure. The | |||
largest one is taken from Schonemann (’04) and represents the adult condition. | |||
They are all on the same scale of enlargement (4.4 diameters) and thus comparison of them shows graphically the amount of growth the labyrinth experiences | |||
during this period. | |||
In addition to this increase in size, there is a change in the form of the cartilaginous labyrinth. The general proportions | |||
1 Schoenemann, A. Die Topographic des menschlichen Gehiirorganes. Verlag Von Bergmann, Wiesbaden, 1904. Plate 2, figure 20. | |||
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Streeter G.L. The Factors Involved in the Excavation of the Cavities in the Cartilaginous Capsule of the Ear in the Human Embryo
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The Factors Involved in the Excavation of the Cavities in the Cartilaginous Capsule of the Ear in the Human Embryo
Department of Embryology, Carnegie Institution of Washington, Baltimore, Maryland
Twelve Figures
The main mass of the cartilaginous capsule of the ear matures into true cartilage when the human embryo reaches a length of 20 to 30 mm., at which time it has acquired what may be considered its adult form with characteristic chambers and openings. From this time on, throughout its whole cartilaginous period, and even after ossification has begun, it undergoes continuous growth, maintaining at the same time, however, its general form and proportions. Such a growth involves both an increase in the surface dimensions of the capsule and a gradual enlargement or excavation of its contained cavities. It is to the manner in which this excavation is accomplished that the writer wishes to call attention and particularly to the factors concerned in its progress whereby a suitable space is always provided for the enlarging membranous labyrinth. The actual amount of increase in size of the labyrinth is graphically pictured in figure 1. The outlines are made so that they show on the same scale of enlargement a series of wax-plate models of the left membranous labyrinth of human embryos having a crown-rump length of 20, 30, 50, 85 and 130 mm., as indicated in the figure. This covers the periodiduring which the otic capsule is in a cartilaginous state. Ossification begins when the fetus has attained a crown-rump length of about 130 mm. The growth from then until the adult condition is reached may be judged by comparing the above with the final stage, labelled adult, which is taken from Schonemann’s reconstruction1 and reproduced here so as to be on the same scale of enlargement as the younger stages. Since the cartilaginous labyrinth corresponds closely in form to the membranous labyrinth, particularly as regards the canals, one can see from figure 1 that there is a progressive increase in the size of the cartilaginous chambers throughout the Whole embryonic period.
Fig. 1 Median views of wax-plate models of the left membranous labyrinth
in human embryos having crown-rump lengths as indicated in the figure. The
largest one is taken from Schonemann (’04) and represents the adult condition.
They are all on the same scale of enlargement (4.4 diameters) and thus comparison of them shows graphically the amount of growth the labyrinth experiences
during this period.
In addition to this increase in size, there is a change in the form of the cartilaginous labyrinth. The general proportions
1 Schoenemann, A. Die Topographic des menschlichen Gehiirorganes. Verlag Von Bergmann, Wiesbaden, 1904. Plate 2, figure 20.
Cite this page: Hill, M.A. (2024, April 24) Embryology Paper - The Factors Involved in the Excavation of the Cavities in the Cartilaginous Capsule of the Ear in the Human Embryo. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/Paper_-_The_Factors_Involved_in_the_Excavation_of_the_Cavities_in_the_Cartilaginous_Capsule_of_the_Ear_in_the_Human_Embryo
- © Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G
