**3. Results**

### **3.1 Von Mises stress and the first principal stress**

**Figure 4** shows the results of von Mises stress in each computation. While the shape of the placenta was largely deformed because of the myometrium contraction and elongation, von Mises stress in the placenta was kept much lower than that in the chorionic and basal plates, marginal region, and myometrium. Also, von Mises stress at these layers fluctuated largely. **Figure 5** shows the results of the first principal stress. As the results of von Mises stress, the first principal stress in the placenta

#### **Figure 4.**

*von Mises stress in the computational model of the human placenta and surroundings, caused by the myometrium elongation and contraction (Mode 1, Mode 2, and Mode 3 (***Table 3***)). The stress distribution is shown by the entire image (right), and the values along each line, indicated by* **Figure 3** *(left).*

*Histological Properties of the Chorionic and Basal Plates and Maintenance of the Mechanical… DOI: http://dx.doi.org/10.5772/intechopen.112935*

#### **Figure 5.**

*The first principal stress in the computational model of the human placenta and surroundings, caused by the myometrium elongation and contraction (Mode 1, Mode 2, and Mode 3 (***Table 3***)). The distribution of the stress is shown by the entire image (right), and the values along each line, indicated by* **Figure 4** *(left).*

was kept lower. The chorionic and basal plates, and marginal region, whose elastic moduli were much higher than the placenta, would prevent changes in the mechanical environment of the placenta. The stable condition in von Mises stress and the first principal stress would promote the effective usage of the perivascular contractile cells in the villous tree and chorionic plate for the fetal and maternal blood circulations.

#### **3.2 Displacement and the first principal strain**

**Figure 5** shows the result of displacement in each computation. The deformation in the placenta at Mode 1 was much larger than that in other cases. The elongation and contraction the myometrium would cause various deformation patterns in the placenta so that the fetal and maternal blood could be stirred. As **Figure 6** shows, the first principal strain showed the same tendency (**Figure 7**).

#### **Figure 6.**

*Displacement in the computational model of the human placenta and surroundings, caused by the myometrium elongation and contraction (Mode 1, Mode 2, and Mode 3 (***Table 3***)). The distribution of the displacement is shown by the entire image (right), and the values along each line, indicated by* **Figure 3** *(left).*
