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Fig. 256. Sagittal section through the head of a human embryo of 4.2 mm (31-34 days)

The pharynx develops from the cephalic end of the primitive gut. This part of the gut is primarily of uniform diameter, is broadly attached by mesoderm to the dorsal body wall, and ends blindly (Fig. 247). When the branchial arches and grooves develop in this (the cervical) region, they affect the gut as well as the periphery of the body. The arches form ridges on the surface of the body (Fig. 85) and at the same time form ridges on the wall of the gut. The grooves form pockets which alternate with the arches (Fig. 256). The pock in the pharyngeal cavity, or inner branchial grooves, are directed outward toward corresponding outer branchial grooves (Fig. 249). The arches are covered externally with ectoderm, internally with entoderm, and are filled with mesoderm. Between the arches, or in the grooves, the ectoderm and entoden are in contact or nearly so. Thus the pharynx is not surrounded by a coelomic cavity.


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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)

Reference

Bailey FR. and Miller AM. Text-Book of Embryology (1921) New York: William Wood and Co.



Cite this page: Hill, M.A. (2024, April 18) Embryology Bailey256.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:Bailey256.jpg

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