File:Frazer1926 fig04.jpg

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Fig. 4. Head of Embryo (10 mm)

Region of precervical sinus in 10mm. embryo. Left side. P,pericardium; I, II, III, pharyngeal arches. The widely open placodal recess of vagus, pl.a.X, is below and behind the narrow duct, pl.d.IX, leading to the glossopharyngeal ganglion. The epipericardial ridge is very prominent below and behind the third arch.

The sinus field in an embryo of 10mm. is shown in fig.4 (P1.I). The placodal areas are now so completely covered and folded in that each is at the enlarged end of a deep pocket or tunnel opening on the surface. The conditions are essentially as in fig. 3 so far as the positions of the openings of the tunnels are concerned, the only difference being in their sizes: they are both smaller, and lead into deeper recesses, that of X being so deep that the fourth arch is no longer actually visible in its floor as in the earlier specimen. The third arch stands out clearly, and is not overlapped or covered in any way by the formation of these placodal pockets.

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Pages where the terms "Historic" (textbooks, papers, people, recommendations) appear on this site, and sections within pages where this disclaimer appears, indicate that the content and scientific understanding are specific to the time of publication. This means that while some scientific descriptions are still accurate, the terminology and interpretation of the developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these terms, interpretations and recommendations may not reflect our current scientific understanding.     (More? Embryology History | Historic Embryology Papers)
Links: Fig. 1. Embryo 4-9 mm | Fig. 2. Semi-schematic pharyngeal region | Fig. 3. Embryo 8 mm | Fig.4. Embryo 10 mm | Fig. 5. Embryo 12 mm | Fig. 6. Embryo 10 mm | Fig. 7. Third Arch | Fig. 8. Laranryngeal Area of Head | Plate 1. Fig.1,3,4


Frazer JE. The disappearance of the precervical sinus. (1926) J Anat. 61(1): 132-43. PMID 17104123.

Cite this page: Hill, M.A. (2024, May 28) Embryology Frazer1926 fig04.jpg. Retrieved from

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© Dr Mark Hill 2024, UNSW Embryology ISBN: 978 0 7334 2609 4 - UNSW CRICOS Provider Code No. 00098G

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