File:ThompsonBrash1923 fig02.jpg

Fig. 2. Diagrammatic reconstruction of the embryonic shield, etc., to show the relation of the primitive streak, the median elevation and the two lateral grooves

The position of the head-process is indicated by a stippled band extending forward from the cranial end of the primitive streak beneath the median elevation. The relation of the amnion and the allantois to the body-stalk is also indicated. Drawn to scale, x about 80.

The reconstruction of the surface of the shield is given in fig. 2, which is drawn carefully to scale. In general shape the dorsal aspect of the shield is oval with its long axis transverse to the long axis of the embryo. The cranial end of the shield is represented by one side of the oval and is bent slightly downwards: the caudal end of the shield appears as a narrowing prolongation of the other side of the oval; it is markedly bent downwards and the projection thus formed is indented in the middle line by the primitive groove. The groove becomes shallower as it is traced forwards to end, a little less than one-third of the distance from the caudal projection to the cranial end of the shield, at the point where the median elevation and the right depression next to be described commence. The whole length of the primitive groove is estimated to be -38 mm.

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Reference

Thompson P. and Brash JC. A human embryo with head-process and commencing arch enteric canal. (1923) J Anat. 58: 1-20. PMID 17103992

Cite this page: Hill, M.A. (2024, April 27) Embryology ThompsonBrash1923 fig02.jpg. Retrieved from https://embryology.med.unsw.edu.au/embryology/index.php/File:ThompsonBrash1923_fig02.jpg

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