446
8 Morphogenesis
Fig. 8.30 3D model for heart tube and foregut formation (undeformed configuration). HF = heart
field; AIP = anterior intestinal portal. From Hosseini et al. (2017)
Fig. 8.31 Differential growth drives diagonal folding in computational model for heart tube and
foregut formation. (a) Normalized growth pattern is same in both layers, but mesoderm grows at
faster rate. Growth increases from blue to red. (b) Ventral view of model at three time points. HT
= heart tube (red); AIP = anterior intestinal portal (green); Y -axis is embryonic midline. Modified
from Hosseini et al. (2017)
The simulation proceeds as follows:
1. FG formation: Orthotropic growth is specified in both layers. The layers have
the same spatial growth pattern with G x < G y (Fig. 8.31a), but the mesoderm
grows at a faster rate. This process causes the SPL to fold diagonally, creating
the FG bounded by endoderm inside the fold (Fig. 8.31b, HH7). Growth in the
Y -direction is constrained to prevent the originally upper edge from passing the
midline, where fusion is simulated by changing the free boundary condition to a
roller support.
2. SPL extension/AIP descension: Gradually increasing tangential contraction
(G y < 1 with increasing modulus) is specified in the AIP border region (green
strip in Fig. 8.31b). This produces a net downward force that, along with specified
longitudinal growth above the AIP, lengthens the SPL (Fig. 8.31b, HH10).
3. HT formation: Pressure is specified between the FG and heart fields, which are
not joined together. The pressure and prescribed circumferential growth expand
the heart fields to create the HT (red in Fig. 8.31b, HH10).
8 Morphogenesis
Fig. 8.30 3D model for heart tube and foregut formation (undeformed configuration). HF = heart
field; AIP = anterior intestinal portal. From Hosseini et al. (2017)
Fig. 8.31 Differential growth drives diagonal folding in computational model for heart tube and
foregut formation. (a) Normalized growth pattern is same in both layers, but mesoderm grows at
faster rate. Growth increases from blue to red. (b) Ventral view of model at three time points. HT
= heart tube (red); AIP = anterior intestinal portal (green); Y -axis is embryonic midline. Modified
from Hosseini et al. (2017)
The simulation proceeds as follows:
1. FG formation: Orthotropic growth is specified in both layers. The layers have
the same spatial growth pattern with G x < G y (Fig. 8.31a), but the mesoderm
grows at a faster rate. This process causes the SPL to fold diagonally, creating
the FG bounded by endoderm inside the fold (Fig. 8.31b, HH7). Growth in the
Y -direction is constrained to prevent the originally upper edge from passing the
midline, where fusion is simulated by changing the free boundary condition to a
roller support.
2. SPL extension/AIP descension: Gradually increasing tangential contraction
(G y < 1 with increasing modulus) is specified in the AIP border region (green
strip in Fig. 8.31b). This produces a net downward force that, along with specified
longitudinal growth above the AIP, lengthens the SPL (Fig. 8.31b, HH10).
3. HT formation: Pressure is specified between the FG and heart fields, which are
not joined together. The pressure and prescribed circumferential growth expand
the heart fields to create the HT (red in Fig. 8.31b, HH10).