RESUMO
We studied human middle ears from Wittmaack's temporal bone collection in the ENT Department of the University of Hamburg. In the 12-week-old fetus, cells from the embryonic middle ear mesenchyme form a tiny semi-circle around the tympanic part of the developing facial nerve. During the following weeks, the production of fibrillar material increases until the facial nerve is surrounded by a dense fibrous semi-canal. Intramembranous ossification starts from ossification centers in the anlage of the membranous facial canal. Bone appears first in the form of spicules surrounded by osteoblasts. At this time, so-called aplastic areas (aplastische Zonen) can be identified between these spicules. Their importance in the latter occurrence of dehiscenses in the mature facial canal is discussed.
