File:Frazer1926 fig01.jpg

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Fig. 1. Head of Embryo (4 to 9 mm)

Head of embryo of 4 to 9 mm, seen from the left. P. pericardium; C. 1, first cervical myotome; Ot.,otocyst.

The precervical sinus, a result of the disproportionate size and growth of the outer pharyngeal arches,begins to show on the surface at an early stage. Fig.1 (PI.I), the head of an embryo of less than 5 mm. in total length, gives a very good idea of this early appearance of the sinus, and of its boundaries. The third and fourth arches are visible in a triangular area, slightly depressed, in front of which the second arch is prominent and its groove very evident. Above and behind is a clearly defined broad area, especially well marked behind. The pericardium is below the sinus, but does not form its lower boundary directly: this is made by a clearly seen epipericardial ridge, which is continuous behind with the caudal boundary, and disappears from view, in front, below the lowest visible part of the third arch. The upper, hinder, and lower boundaries are thus continuous with each other round the field of the sinus, and require more particular examination.

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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 29) Embryology Frazer1926 fig01.jpg. Retrieved from

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