Under Pneumatization (of gr. Πνεῦμα [ pneuma ] "breath", "breathing") refers to the formation of air-filled cavities in originally relatively dense bone, both in the course of evolutionary history (phylogeny) and in the course of individual development (ontogeny). Such modified bones are also called "air-filled bones" ( Ossa pneumatica ). They are represented to different extents among the various recent and extinct groups of terrestrial vertebrates and for reasons that are not always obvious. For example, while the weight saving is an obvious reason for the heavily pneumatized skeleton of birds , the point of the rather minor pneumatization of the human skull, which only accounts for around two percent weight saving, is less clear.
Pneumatization of the human skull
The pneumatic cavities of the skull develop by the mucosal epithelium of the nose or the middle ear is baggy in the mesoderm pushes or between the compact cortical layers of the bones.
The result of this process is, on the one hand, the paranasal sinuses , whose final development in humans is only achieved when the skull has finished growing between the ages of 20 and 25. Some animals have no sinuses (seals, whales), in others they reach a much larger extent than in humans.
The pneumatization of the temporal bone emanating from the middle ear is largely completed by the age of five to six. The result of this process are the pneumatic cells, especially in the mastoid process . They are small cavities, lined with mucous membrane, which are connected to each other and as a whole with the mastoid antrum and thus with the middle ear through openings of different sizes . The extent of the pneumatization of the temporal bone can be very different, there are temporal bones with almost completely missing ("inhibited") pneumatization, which is mostly to be seen as a consequence of frequent otitis media in childhood. On the other hand, the pneumatization can extend far up into the temporal bone scale ( pars squamosa ), forward into the zygomatic process ( processus zygomaticus ) and into the tip of the temporal bone pyramid . It can be in the mastoid typically individual cell groups or cell lines differ, bearing different names, such as angle cells threshold cells, terminal cells, etc. Accordingly, in extensive pneumatization squamous cells (in the squama) Zygomaticuszellen (the zygomatic process), perilabyrinthäre cells (around the maze located ) and pyramidal tip cells.
Pneumatization of the long bones in birds
In birds, the large tubular bones such as the humerus , the raven bone , the pelvis , the sternum and the vertebrae are also pneumatized, and in some species the femur , the shoulder blade and the collarbone . This pneumatization is caused by bulges in the air sacs that extend into said bones.
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