Fig. (3).

(A) The “facial block” showing the effects of angular invariance between the back of the face (summarized by the PM plane) and the top of the face, which is also the bottom of the anterior cranial base (S-FC). Changes in cranial base angle (NHA-BaS or alternatively S-FC-BaS) cause the top and back of the face to rotate together around an imaginary axis through the PM point [12]. Illustration from [12]. (B) Osteocutaneous ligaments that originate from periosteum and insert directly into dermis (zygomatic and mandibular ligaments are shown; zygomaticus minor and major muscles, masseteric cutaneous ligaments and risorius are also shown). Note the modiolus as a confluence of muscles located at the angle of the mouth. Illustration from [54]. (C) Skull in norma lateralis shows the asymmetric growth of the spheno-occipital synchondrosis. Tension on the aponeurosis (arrows at glabella and occipital nuchal line) are expressed as an inverted V with the net force at the center of the skull, superior to the occipital condyle (large arrow). This is expected to create a lever system (dark lines) pivoting at the large arrow and extending to the smaller arrows. These are the effective forces of the muscles on the dorsal and ventral skull surface. (D) The divergence of the facial planes (sella-nasion at the top and then descending; orbitale-porion or the Frankfort horizontal; palatal plane; occlusal plane; mandibular plane).