Back of tongue looking forward
Middle of tongue cut in half (sagittal view)
There feels to be a difference in how I usually use both the left and right backs of the tongues. I believe it to be to be echoed with my jaw position. When I eat with a spoon the right side is given a slight advantage getting to the food as the spoon gets closer to my mouth. If I reverse the sides and eat with my left hand I not only get a scapular reversal resistance but a mandible reversal resistance due to my habitual eating movements. In my normal right hand eating it would seem to be an advantage to pull the right side back as the spoon gets closer but I think the right side of jaw and tongue go forward to meet the spoon. The TMJ joint allows for limited moment in three planes (see below) with the left side of the jaw musculature doing the opposite of the right side at times. It feels like I have a posture of the tongue that gives the right side an advantage. It is more subtle and complicated than it would seem as it pulls in other structures to accommodate the position. To reverse the position of the tongue it is almost like I swallow the right tongue slightly to allow the left to lengthen from the anterior jaw all the way to the clavicle.
Movements.—The movements permitted in this articulation are extensive. Thus, the mandible may be depressed or elevated, or carried forward or backward; a slight amount of side-to-side movement is also permitted. It must be borne in mind that there are two distinct joints in this articulation—one between the condyle and the articular disk, and another between the disk and the mandibular fossa. When the mouth is but slightly opened, as during ordinary conversation, the movement is confined to the lower of the two joints. On the other hand, when the mouth is opened more widely, both joints are concerned in the movement; in the lower joint the movement is of a hinge-like character, the condyle moving around a transverse axis on the disk, while in the upper joint the movement is of a gliding character, the disk, together with the condyle, gliding forward on to the articular tubercle, around an axis which passes through the mandibular foramina. These two movements take place simultaneously, the condyle and disk move forward on the eminence, and at the same time the condyle revolves on the disk. In shutting the mouth the reverse action takes place; the disk glides back, carrying the condyle with it, and this at the same time moves back to its former position. When the mandible is carried horizontally forward, as in protruding the lower incisor teeth in front of the upper, the movement takes place principally in the upper joint, the disk and the condyle gliding forward on the mandibular fossa and articular tubercle. The grinding or chewing movement is produced by one condyle, with its disk, gliding alternately forward and backward, while the other condyle moves simultaneously in the opposite direction; at the same time the condyle undergoes a vertical rotation on the disk. One condyle advances and rotates, the other condyle recedes and rotates, in alternate succession.