8.1 The Carnegie stages

Synoptic table of the Carnegie stages 7 - 10

Stage 7

Approx. 19th day: Dorsal view

0.4 mm

1 2 3 4 Yolk sac Primitive streak Primitive node Embryonic disk

Characteristic signs:Mesoblast immigration Chordal process Neural plate Genesis of the blood vessel system and formation of blood

Stage 8

Approx. 23th day

0.5 - 1.5 mm

1 2 3 4 Body stalk Primitive streak Embryonic disk Cut edge of the amnion

Characteristic signs:Pear shaped embryo Axial process Neurenteric canal Neural groove forming

Stage 9

Approx. 25th day

1.5 - 2.5 mm

`1 2 3`	`Primitive streak and primitive groove Neural folds Cut edge of the amnion`

`4 5`	`Neural groove Somites`

Characteristic signs:Embryo with somites (1-3 somites) Pharyngeal membrane Neural groove Caudal eminence Intraembryonic coelom Cardiac primordium, septum transversum Placode and auditory pit

Stage 10a, 10b

Approx. 28th day

2 - 3.5 mm

`1 2a 3 4`	`Cut edge of the amnion Neural groove Neural folds Somites`

`2b 2c 2d 5`	`Neural tube Caudal neuropore Rostral neuropore Yolk sac`

Characteristic signs:Lateral folding Closure of the neural groove into a neural tube The 2 first pharyngeal arches appear Ophthalmic vesicle Rupture of the pharyngeal membrane 4 - 12 somites

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