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Fig. 2 | EvoDevo

Fig. 2

From: Outflow tract septation and the aortic arch system in reptiles: lessons for understanding the mammalian heart

Fig. 2

Development of the AP septum in chicken HH26–28. a The AP septum between Pu (6 + 6) and Ao channels (3 + 3 + 4 + 4). WT1 staining (brown) in the epicardium and mesenchymal second heart field cells. b slightly more distal, the Pu is separated into the left and right PAA6 and the Ao channel in the right PAA4 and separate PAA3. Note that the lumen of the left PAA4 has disappeared. c The area of apoptosis is continuous with the massive apoptosis in the AP septum (arrows and inset, see also Fig. 4e). d In HH28, the lumen of the left PAA4 (4L) is nearly occluded and the vascular smooth muscle cells (negative in this WT1 staining) are still visible. Note the elaborate WT1 staining (brown) between the vascular segments. e Amira reconstruction of HH28 seen from ventral showing the lumina of the arterial trunks. la left atrium, ra right atrium, myo ventr myocardium ventricle f Same embryo, the fused OFT cushions (blue) contain a groove for the condensed mesenchyme (*) running between PAA6 (6) and the stem of PAA4R (4R) and PAA3 (3). Note that the lumen of PAA4L (4L) is interrupted and does not reach the heart anymore. OFT cu fused outflow tract cushions, ventr lumen ventricle

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