part_of part of part of ligament periodontium periodontal ligament https://upload.wikimedia.org/wikipedia/commons/d/dc/The_Periodontium.jpg paradentium EMAPA:35679 BTO:0001020 periodontal fiber SCTID:245775004 peridontal ligament fiber fibra periodontalis peridontal ligament fibre odontoperiosteum FMA treats periodontium and periodontal ligament as the same; it has a separate class desmodentium, which we place here even though it is classified as fetal in FMA UBERON:0008266 periodontal fibre MESH:D010513 desmodontium peridontal fibre peridontal ligament PDL peridontal fiber peridontium Wikipedia:Periodontal_fiber peridontal membrane alveolar periosteum FMA:56665 The fibrous connective tissue that surrounds the root of a tooth, separating it from and attaching it to the alveolar bone. It extends from the base of the gingival mucosa to the fundus of the bony socket, and its main function is to hold the tooth in its socket[BTO]. It consist of cells, extracellular compartment of fibers. The cells are fibroblast, epithelial, undifferentiated mesenchymal cells, bone and cementum cells. The extracellular compartment consists of collagen fibers bundles embedded in ground substance. The PDL substance has been estimated to be 70% water and is thought to have a significant effect on the tooth's ability to withstand stress loads[WP][BTO:0001020, Wikipedia:Periodontal_fiber, https://github.com/obophenotype/uberon/issues/21]. The collagen fibers, running from the cementum to the alveolar bone, that suspend a tooth in its socket; they include apical, oblique, horizontal, and alveolar crest fibers, indicating that the orientation of the fibers varies at different levels[http://www.drugs.com/dict/desmodentium.html]. periodontium alveolodental ligament peridental membrane GAID:1259 CALOHA:TS-0763 alveolodental membrane The fibrous connective tissue that surrounds the root of a tooth, separating it from and attaching it to the alveolar bone. It extends from the base of the gingival mucosa to the fundus of the bony socket, and its main function is to hold the tooth in its socket[BTO]. MA:0002467 skeletal ligament neural crest-derived structure