Template:O'Rahilly1963 Carnegie embryo table

Online Editor
Stage No. Somites 9 1878 2 10 3709 4 391 8 1201 8 5074 10 3710 11 3707 12 9870 12 11 7611 16 470 17 5072 17 8116 17 12 8943 22 8505b 23 9154 24 6097 25 7852 25 8942 25 5923 28 7724 29	Stage No. Somites 13 836 4.0 7889 4.2 9297 4.5 8581 4.8 8372 5.6 14 8308 5.85 8999 6.0 6503 6.3 8552 6.5 8314 8.0 15 8997 9.0 16 8773 13.0 17 8998 11.0 8789 11.7 18 8355 15.0 9247 15.0
Otic Vesicle in Staged Embryos Stage 9 - (1-3 somites) (Plate 1, fig. A) The otic region can first be distinguished in the embryo (No. 1878) of two somites as a thickening on the lateral aspect of the neural fold (Text-fig. 1). It is lined by a basement membrane that is continuous with that of the rhombencephalic neural groove. Stage 10 - (4-12 somites) (Plate 1, fig. B) The nuclei of the otic plate occupy mostly a basal position, leaving a superficial cytoplasmic zone termed the marginal velum. The velum appears to be covered by a terminal bar net (as is the lens at a later stage) and a brush border. Mitotic figures, in this and subsequent stages, are found in the superficial (later central) portion of the plate (as is also the case in the wall of the neural groove and tube). The first indication of invagination of the otic plate is ob- served at ten somites. Neural crest cells, recognizable in this region first at four somites, delaminate from the wall of the neural groove and proceed laterally and ventrally. They are presumed to be the facial, or the so-called acousticofacial, crest. Stage 11 - (13-20 somites) (Plate 1, fig. C) The otic pit forms in the otic plate during this period, in a manner reminiscent of the formation of the lens pit three stages later (Text-fig. 2). Stage 12 - (21-29 somites) (Plate 1, fig. D) The otic vesicle is forming and its cavity communicates with the surface by a narrowing pore. Stage 13 - (30 or more somites; approximately 4-6 mm) (Plate 1, figs. E, F , and Plate 2, figs. G, H) The otic pit becomes closed from the surface to form the otic vesicle, or otocyst, the dorsomedial portion of which can be distinguished as the endolymphatic appendage. Stage 14 - {5-7 mm) As usual, the mitotic figures are placed centrally, that is, near the cavity of the vesicle. Remnants of the connecting stalk may still be seen in some speci- mens. The endolymphatic appendage is set off from the future utricular portion of the vesicle by a developing fold. Stage 15 - (7-9 mm) The utriculo-endolymphatic fold becomes more pronounced. Ventro-medially, the tip of the vesicle represents the cochlear duct. The thickness of the wall of the vesicle varies from one portion to another; the wall of the endolymphatic appendage is becoming thinner. Stage 16 (7-11 mm) - Thickenings in the wall of the main, or vestibular, portion of the vesicle presage the appearance of the semicircular ducts. Stage 17 - (11-14 mm) (Plate 2, fig. I) - Portions of the wall of the vestibular part of the. otic vesicle become thinner and approximated as a prelude to the cellular disintegration that takes place during the formation of the semicircular ducts at the next stage. Stage 18 - (12-17 mm) - During the formation of each of the semicircular ducts from thickened areas of epithelium, the adjacent portions of the epithelium become thinned, the cells lose their individuality, and their basement membrane disappears, so that the tissue merges with the underlying mesoderm (Plate 2, fig. K). Obliteration of the corresponding portions of the cavity of the otic vesicle ensues, so that the hollow ledges are converted into semicircular tubes, and so that continuity of the remaining epithelium and also of the remaining basement membrane is immediately restored. The wall of the semicircular duct opposite the site of sealing is thickened considerably (Plate 2,fig.L).
Reference:O'Rahilly R. The early development of the otic vesicle in staged human embryos. (1963) J Embryol Exp Morphol., 11: 741-55 PMID 14081992