From Embryology

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Fig. 86. Human embryo of 4 mm

Rabl, from Kollmann's Atlas.

An embryo of 4 mm. is shown in Fig. 86. All the flexures are accentuated, so that the head and tail are close together. The fourth branchial arch has appeared behind the third groove and a fourth groove behind the fourth arch. The small structure behind the fourth groove may be the rudimentary fifth arch. The arches diminish rather uniformly from the first to the last. The rudiment of the eye is visible on the side of the forebrain region as a circular eminence surrounded by a slight groove. The heart protuberance is strikingly prominent. Certain new features have appeared at 'this stage, the limb buds. The fore-limb bud is a rounded eminence opposite the anterior part of the dorsal flexure; the hind-limb a similar structure opposite the sacral flexure. The limb buds, as tar as surface appearance goes, are Simply outgrowths from the body wall starting as small rounded eminences which, as development proceeds, become larger and finally differentiated into the various parts of the extremities.

Links: Fig. 86 in text

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

Cite this page: Hill, M.A. (2024, June 23) Embryology Bailey086.jpg. Retrieved from

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