And so, we 3D-print three pieces with joints that represent the elbow joint and the wrist joint.

因此我们3D打印了三个由模拟的肘关节和踝关节连接的装置。

When you see the apple, your brain's motor center activates the appropriate muscles, allowing you to reach out with your arm, grab it with your hand, bend your elbow joint, and bring it to your mouth.

当你看见苹果，大脑的运动部分激活合适的肌肉，使你伸出手臂，用手抓住它，弯曲手肘，把它送到你嘴中。