File:Bailey087.jpg

Fig. 87. Human embryo with twenty-seven primitive segments (7 mm, 26 days)

Mall.

In a 7 mm embryo described by Mall (Fig. 87), the flexures are slightly more accentuated than in the 4-mm stage. The branchial arches and grooves are still prominent. The first groove, of which the dorsal part marks the site of the external auditory meatus, is at this time particularly well developed. The eye is a stronger feature than in the preceding stage. The distinct depression in front of the first arch is the nasal fossa. The limb buds are larger than in the 4 mm embryo. The general curvature of the embryo is so sharp at this stage that the rudimentary tail is almost in contact with the head.

Online editor - The term "branchial arch" in human embryos is now more commonly called a "pharyngeal arch".

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Pages where the terms "Historic Textbook" and "Historic Embryology" appear on this site, 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 interpretation of developmental mechanisms reflect the understanding at the time of original publication and those of the preceding periods, these interpretations may not reflect our current scientific understanding. (More? Embryology History)

Reference

Bailey, F.R. and Miller, A.M. (1921). Text-Book of Embryology. New York: William Wood and Co.

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