In the anterior part are present the pro-anmnion, which is a small and comparatively more translucent region of area pellucida and is characterised by the absence of mesoderm.Ħ. At this stage the dark peripheral area opaca and central translucent and colourless area pellucida are distinctly visible.ģ. The primitive streak gives rise to an out-growth, the notochord immediately below the primitive groove.ġ. The primitive streak and neural groove is separated by a thickening-the Hensen’s node having a small depression in the centre-the Hensen’s pit.ħ. In the anterior half of area pellucida, in the middle, runs a neural groove bound by neural folds.Ħ. The primitive groove is being bound by primitive folds.ĥ.
In the middle of area pellucida, in the posterior half, runs a primitive streak having a primitive groove through its centre. In the anterior part is present the pro-amnion, which is a small and comparatively more translucent region of area pellucida and is characterised by the absence of mesoderm.Ĥ. At this stage the dark peripheral area opaca and central translucent area pellucida are distinctly visible.ģ. Caudal end of the streak is that which lies close to the area opaca.
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