鼓膜の発育

抄録

Developmental anatomy of the tympanic membrane and its relation with the malleus handle was studied using fetal temporal bone specimens. During 16th week of gestation the intermediate mesodermal layer which consist of two laminas-radial layer laterally and circular layer medialy-originate around the tympanic ring as loose connective tissue. The inner circular layer hold the malleus handle and fuses with the periosteum (or perichondrium). The outer radial layer which is thicker than the outer circular layer contains copious blood vessels. After 30th week of gestation conjunction between malleus handle and inner circular layer become loose and lost except outer surface of the malleus handle. Only at the tip of the malleus periosteum is thick and hold by the circular layer which seems to become the umbo.