The functional significance of the position of the centre of rotation for jaw opening and closing in the rabbit.
The functional significance of the position of the centre of rotation for jaw opening and closing in the rabbit.
复制标题
兔子开合颌旋转中心位置的功能意义。
作者：
W. Weijs;J. Korfage;G. Langenbach
在兔中，颌骨的张开和闭合伴随着髁突的前伸和后缩。因此，运动的旋转中心(CR)位于下颌升支的下部，远远低于髁突。这个位置是稳定的，与被咀嚼的食物的类型和动物的年龄无关。升支后缘软组织的地形与运动模式相适应。面神经在CR平面上横穿颅骨和下颌骨之间的间隙。腮腺位于髁状突和CR之间的支后部；在CR下方，腺体被疏松的脂肪组织取代。计算机模型被用来证明CR的位置决定了大咬肌和翼内侧肌的伸展程度。使用通过尸检测量获得的肌肉被动弹性行为的参数，可以表明正常的CR位置使肌肉拉伸和被动弹力最小化。即使是CR的微小向上移位，也会在闭口处引起相当大的阻力，与自然咀嚼时达到的阻力相当。第二，由于纤维长度和等长张力的相互关系，肌肉伸展增加的第二个不太明显的影响是最大可能的主动闭合力急剧下降。在幼年动物中，肌肉纤维相对较长但僵硬；在成年动物中，它们较短，但更顺从。在这两个年龄段，CR的位置都是这样的，即最大限度地减少咀嚼肌和翼骨内侧伸展。颞下颌关节的高位置确保了上述肌肉的最大杠杆作用。通过将反作用力的作用点(关节)与旋转轴的位置分开，可以同时实现最大的杠杆作用和最小的闭口肌长度变化。进一步认为，弹性肌力在决定CR的位置中起作用。
In the rabbit, jaw opening and closing occurs in combination with condylar protrusion and retraction. Consequently the centre of rotation (CR) for the movement lies in the inferior portion of the ascending ramus of the mandible, far below the condyle. This location is stable and independent of the type of food being chewed and the age of the animal. The topography of the soft tissues at the posterior border of the ramus is adapted to the movement pattern. The facial nerve crosses the space between skull and mandible at the level of the CR. The parotid gland lies behind the ramus between condyle and CR; below the CR, the gland is replaced by loose adipose tissue. A computer model was used to demonstrate that the location of the CR determines the amount of stretch of the large masseter and medial pterygoid muscles. Using parameters for passive elastic behaviour of muscle, obtained by postmortem measurements, it can be shown that the normal CR position minimises muscle stretch and passive elastic forces. Even a small upward displacement of the CR causes a significant amount of resistance in the jaw-closers at gapes comparable to those reached in natural mastication. A second, less dramatic effect of increased muscle stretch is a sharper decline of maximum possible active closing force, due to the interrelationship of fibre length and isometric tension. In young animals, the muscle fibres are relatively long but stiff; in adults they are shorter, but more compliant. In both ages the CR is located in such a way that masseter and medial pterygoid stretching is minimised. The high position of the temporomandibular joint ensures a maximal leverage for the muscles mentioned above. By separating the point where the reaction forces apply (the joint) from the location of the rotational axis, maximum leverage and minimal length changes of the jaw-closing muscles are achieved simultaneously. It is further suggested that elastic muscular forces play a role in determining the position of the CR.
影响因子：
3.3
作者：
POWELL, PL;ROY, RR;EDGERTON, VR
通讯作者：
EDGERTON, VR
二腹肌肌腱切断术对兔子下颌张开的影响。
影响因子：
3
作者：
Weijs,WA;Muhl,ZF
通讯作者：
Muhl,ZF