Ossification - ossification

The process by which bone tissue develops and is formed in the body. It is treated as a synonym for bone formation that accompanies growth. When describing a pathological condition, it is often used to mean "ossification," and refers to the transformation of mesenchymal tissue, usually fibrous connective tissue or cartilage, into bone tissue. Also called ossification, it occurs when repeated stimulation is applied to degenerated or necrotic tissue or cartilage, accompanied by calcium deposition.

Normally, the formation of bone tissue where there is no bone is called ectopic ossification, and ectopic ossification in soft muscle tissue is called myositis ossificans. In particular, when ossification occurs due to crushing of muscle tissue or bleeding within the tissue caused by trauma, ectopic bone tissue is formed, resulting in traumatic myositis ossificans. When ossification occurs in spinal ligaments such as the posterior longitudinal ligament and ligamentum flavum (ossification of the posterior longitudinal ligament, ossification of the ligamentum flavum), it can cause compressive myelopathy, which puts pressure on the spinal cord and causes sensory and motor disorders. When ectopic bone forms at the attachment site of a tendon such as the Achilles tendon, and is accompanied by pain, it is called tendon ossification, and there is also idiopathic hyperostosis, in which ossification extends to the attachment sites of tendons and ligaments throughout the body, with an unknown cause. Some ossification conditions are thought to have a genetic predisposition.

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Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

生体において骨組織が発生し形成される過程。成長に伴う骨形成と同義に扱われる。病態を表す場合は「骨化症」の意味で使われることが多く、間葉性組織、多くは線維性結合組織あるいは軟骨が骨組織に変化することをいう。化骨ともいい、変性あるいは壊死(えし)した組織や軟骨に繰り返し刺激が加わり、石灰の沈着などを伴っておこる。

　本来、骨のないところに骨組織が形成されることを異所性骨化、筋肉の軟部組織に異所性骨化を生じる場合を骨化性筋炎とよぶ。とくに外傷が原因で筋組織の挫滅(ざめつ)や組織内の出血をおこして骨化した場合は、異所性骨組織の形成により外傷性骨化性筋炎となる。後縦靭帯(こうじゅうじんたい)や黄色靭帯などの脊柱(せきちゅう)靭帯に骨化を生じると（後縦靭帯骨化症、黄色靭帯骨化症）、脊髄(せきずい)を圧迫し感覚および運動に障害を伴う圧迫性脊髄症などとなる。アキレス腱(けん)など腱の付着部に異所性骨が形成され疼痛(とうつう)などを伴うものは腱骨化症とよばれ、全身の腱や靭帯の付着部に骨化が及ぶ原因不明の特発性過骨症などもある。骨化の病態のなかには遺伝的素因が指摘されるものもある。

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