The formation and deposition of a hard protein called keratin in the epithelial cells of vertebrates. This is also called keratinization. Daughter cells produced by division of epithelial basal cells accumulate keratin as they move to the outside of the body, and a large amount of keratin is produced by the time they reach the surface and die. This keratin covers the epithelium in a layer, providing mechanical protection for the epithelium. The structures on the surface of vertebrates, such as hair, bird feathers, and reptile scales, are formed as special forms of keratinization. [Shigeo Takeuchi] Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend |
脊椎(せきつい)動物の上皮細胞内でケラチンとよばれる硬タンパク質が生成沈着すること。角化ともいう。上皮の基底細胞の分裂によって生じた娘(じょう)細胞が体外側へ移動しつつケラチンを蓄積し、表側に達して死ぬまでに多量のケラチンがつくられている。このケラチンはそのまま上皮を層状に覆い、上皮の機械的保護の役を果たす。脊椎動物の体表の構造物である毛、髪、鳥の羽毛、爬虫(はちゅう)類の鱗(うろこ)などは角質化の特別な形としてつくられる。 [竹内重夫] 出典 小学館 日本大百科全書(ニッポニカ)日本大百科全書(ニッポニカ)について 情報 | 凡例 |
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