The Pine ( gr Γνάθος, gnathos; Bavarian, Austrian colloquially: the jaw), which is used for food intake in most vertebrates and therefore usually is dentate. It consists of the upper jaw ( maxilla Latin ) and the lower jaw ( mandible lat ). The teeth are in the jaw in the tooth sockets (alveoli ) via a Gomphosis ( impaction ) anchored.
In mammals, the lower jaw in the jaw joint ( temporomandibular joint ) is movable on the temporal bone ( temporal bone ) attached. During embryonic development, the TMJ is still elsewhere ( see below in birds ), which is why it is referred to as a secondary comparative- anatomical TMJ. Upper and lower jaws are so connected with each other only indirectly. The upper jaw is immobile in mammals, among them, only the lower jaw is moved by the muscles of mastication. The two jaw halves are completely fused.
The lower jaw of birds ( Aves) is composed of several fused bones. One of these, the os articular corresponds to the articular process of the lower jaw of mammals. The cranial counterpart forms in birds the os quadratum. This skull bone is still involved in the mammal in the formation of the primary jaw joint, but (Hammer, Malleus ) is shifted into the middle ear then as one of the ossicles, so that a secondary TMJ is necessary. Another special feature of birds is that even the maxilla ( upper beak ) secured by a connective tissue elastic zone to move the skull and is therefore actively involved in the beak opening. The jaw of the recent birds is toothless.