Chin K, Kurian R, Saunders J C
Department of Otorhinolaryngology: Head and Neck Surgery, University of Pennsylvania Philadelphia 19104 USA.
J Morphol. 1997 Sep;233(3):257-66. doi: 10.1002/(SICI)1097-4687(199709)233:3<257::AID-JMOR5>3.0.CO;2-0.
The surface area of the chick (Gallus domesticus) tympanic membrane (TM) increases by as much as 400% from hatching to 70 days of age (Cohen et al. [1992] J. Morphol. 212:187-193). The present study is concerned with the processes that contribute to this remarkable size increase. Middle-ear specimens were harvested in embryos aged between E10 and E18, and in post-hatch animals between days P1 and P57. Specimens were embedded in paraffin, cut in serial sections, stained for collagen fibers, and examined with light microscopy. Four locations were examined in each specimen: the anterior and posterior perimeter of the TM, the TM, over the extra-stapedius, and the TM at the tip of the extra-columella. The thickness of the epithelial, respiratory, and lamina propria layers was measured at each location. The radial collagen fibers in the lamina propria were also counted at each location, and fiber density per square micrometer was determined at each age. Thickness of the epithelial and respiratory layers remains relatively constant throughout development in all areas of the TM, whereas the lamina propria at the extra-columella and extra-stapedius continues to thicken with increasing age. Collagen density also increases during development, and this is attributed to an increase in fiber number and a reduction in the space between fibers. The results suggest that collagen may be synthesized first in the central regions of the TM and then later in more peripheral areas of the TM.
雏鸡（家鸡）鼓膜（TM）的表面积从孵化到70日龄增加了多达400%（Cohen等人，[1992]《形态学杂志》212:187 - 193）。本研究关注的是导致这种显著尺寸增加的过程。在胚胎期E10至E18以及孵化后第1天至第57天的动物中采集中耳标本。将标本嵌入石蜡中，切成连续切片，对胶原纤维进行染色，并用光学显微镜检查。在每个标本中检查四个部位：鼓膜的前后边缘、镫骨肌上方的鼓膜、镫骨外侧突上方的鼓膜以及镫骨小柱尖端处的鼓膜。在每个部位测量上皮层、呼吸层和固有层的厚度。还在每个部位计数固有层中的径向胶原纤维，并确定每个年龄段每平方微米的纤维密度。在鼓膜所有区域的整个发育过程中，上皮层和呼吸层的厚度保持相对恒定，而镫骨小柱和镫骨外侧突处的固有层随着年龄增长持续增厚。在发育过程中胶原密度也增加，这归因于纤维数量的增加和纤维间空间的减小。结果表明，胶原可能首先在鼓膜的中央区域合成，然后在鼓膜的更多周边区域合成。
