Incisive bone

The premaxillary bone ( premaxillary bone, premaxilla, premaxilla ) is a paired bone of the facial skeleton and adjacent to the nasal bone ( nasal ) and the upper jaw bone ( maxilla ). In man, these bones fused before birth with the maxillary bone and is therefore not listed as a separate bone in the adult. In the other mammals, the suture ( suture incisiva ) to the upper jaw bone remains visible long. This is due to that the front face region in humans is greatly reduced, so that the upper jaw is stressed in compression only vertically ( Marinelli 1929).

On Zwischenkieferbein a body (corpus ) and three extensions are distinguished:

• Alveolar process ( alveolar process ): It is home to the alveoli of the maxillary incisors ( incisors ) of each side, unless there are no such teeth (ruminants ). Hence the Latin name premaxilla.
• Nasal process ( nasal process ): backward and upward, forms ( exceptions: Human, predators ) with the nose a forwardly open slot ( notch nasoincisiva )
• Palatine process ( palatine process ) forms the front part of the hard palate. Between the two incisive bones a gear, the ductus incisivus that connects the mouth and nasal cavity runs.

The paired premaxilla was in addition to the "old" upper jaw of sharks in the Osteichthyes of several toothed mouth rim bone (→ Amia ). In abgeleiteteren Teleostei it is for the sole carrier of teeth in the upper oral cavity. The derived Rhipidistia of terrestrial vertebrates the premaxilla can not obtain such supremacy because of snatching in much thinner air medium and chewing ( risk of breakage).

Johann Wolfgang von Goethe took lay claim to have discovered the already known in animals Zwischenkieferbein 1784 together with Justus Christian Loder in anatomy tower in Jena in the human embryo. He had not known that the bone had previously been described several times, most recently in 1780 by the French physician Félix Vicq d' Azyr. The existence of the premaxillary bone in ontogeny ( individual development ) of the people is an indication of the common phylogeny ( evolutionary history ) of humans and other animals and thus for evolution.