Category:Meyer 300

From Embryology

This Embryology category includes pages and images that relate to the historic human “Meyer 300” embryo. This historic early human embryo was classified as Carnegie stage 12 during Week 4, GA week 6.


Human Embryo No. 300
Collection of Professor R. Meyer, Berlin. Carnegie stage 12
Desig. Size Age Body form Primitive streak Primitive segments Chorda Nervous system Eye Ear Nose Hypophysis Mouth Digestive trac, liver and pancreas Branchial pouches, threoid thymus, trachea and lungs Urogenital system Heart and vessels Integument Skeleton Extremities Amnion Allantois Remarks
7
N.T. Fig. VI 1, VI r ind VI v.
Gr. L. 2.5 mm. Remains of primitive streak. Cloacal membrane. 23 pairs of primitive segments. Chorda separated from entoderm, Anterior neuropore closed. but its position still recognizable. Medullary canal stili wide open for a stretch caudally. Roof of 4th vent, beginning to thin out. Neuromeres. Trigeminus and acustico-facialis ganglia distinct. Optic vesicles. Mesoderm between ectoderm and optic vesicle, Auditory vesicle almost closed (open through 4 or 5 sections of 5μ). Ductus endolymphaticus not yet visible. Anlage doubtful. Pharyngeal membrane just torn, still abundant remains of it. Intestine still communicates widely with the yolk sack. Liver a thick-walled sack from which the trabeculse are beginning to bud. The 3 anterior branchial pouches reacts the ectoderm; the 4th, though formed, does not. Thyreoidea mediana formed. Pulmotracheal groove. The paired condition of the pulmonary anlage already indicated. Rudimentary "pronephric anlage" Heart S-shaped. Allantoic duct The embryo was obtained by operation.
Remarks

Abundant mitoses in the embryo. Fixation: ? Stain: Borax carmine. Sections: 5 μ. The embryo was modelled by Dr. Peter Thompson (1907) Also see Meyer (1904)

Reference: Keibel F. and Elze C. Normal Plates of the Development of the Human Embryo (Homo sapiens). (1908) Vol. 8 in series by Keibel F. Normal plates of the development of vertebrates (Normentafeln zur Entwicklungsgeschichte der Wirbelthiere) Fisher, Jena., Germany.
Cited in: 1912 Human Embryology and

Thompson P. Description of a human embryo of twenty-three paired somites. (1907) J Anat Physiol, 41(3):159-71. PMID 17232726; Meyer, Rob., Ueber die Beziehung der Umierenkanalchen zum Coelomepithel, etc., Anat. Anz., Vol. 25, 1904

1908 Embryo Tables: Klb (stage 10) | Pfannenstiel III (stage 11) | Meyer 300 (stage 12) | Strahl 4mm (stage 13) | Hertwig G31 (stage 14)



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Fig. 317. Pharynx of the embryo Meyer 300 (Normentafel Xo. 7, 23 pairs of primitive segments, 2.5 mm vertex-breech length) seen from the ventral surface. The closing membranes of the gillclefts are outlined in black.

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