Ladhams A, Pickles J O
Department of Physiology and Pharmacology, University of Queensland, Australia.
J Comp Neurol. 1996 Mar 4;366(2):335-47. doi: 10.1002/(SICI)1096-9861(19960304)366:2<335::AID-CNE11>3.0.CO;2-O.
The organ of Corti and macula lagena were studied by scanning and transmission electron microscopy in two species of monotreme, the platypus and echidna. In both species, the organ of Corti had a fundamentally mammalian conformation, with distinct outer and inner hair cells, separated by a tunnel of Corti. However, unlike eutherian mammals, the monotremes had three or four rows of pillar cells, and four to five rows of inner hair cells. The organ of Corti was much shorter than in eutherian mammals, at 4.4 mm (platypus), and 7.6 mm (echidna). While the total number of outer hair cells (3,350 platypus, 5,050 echidna) was many fewer than in most eutherian mammals, the total number of inner hair cells (1,600 platypus, 2,700 echidna) was comparable with that in eutherian mammals. The stereocilia on both inner and outer hair cells underwent a systematic change in orientation across the cochlear duct, with those nearest the tunnel of Corti having their axis of symmetry oriented transversely across the duct, and those on the outer edge of the organ having the axis oriented nearly longitudinally along the duct. The macula lagena had signs of a vestibular epithelium, with tall bundles of stereocilia, a division into areas with bundles of opposing orientation and type I and type II hair cells.
通过扫描电子显微镜和透射电子显微镜对鸭嘴兽和针鼹这两种单孔目动物的柯蒂氏器和瓶状囊斑进行了研究。在这两个物种中，柯蒂氏器具有基本的哺乳动物构造，有明显的外毛细胞和内毛细胞，由柯蒂氏隧道分隔。然而，与真兽类哺乳动物不同的是，单孔目动物有三排或四排柱细胞，以及四排到五排内毛细胞。柯蒂氏器比真兽类哺乳动物的要短得多，鸭嘴兽的为4.4毫米，针鼹的为7.6毫米。虽然外毛细胞的总数（鸭嘴兽为3350个，针鼹为5050个）比大多数真兽类哺乳动物少得多，但内毛细胞的总数（鸭嘴兽为1600个，针鼹为2700个）与真兽类哺乳动物相当。内毛细胞和外毛细胞上的静纤毛在整个耳蜗管中方向发生系统性变化，最靠近柯蒂氏隧道的静纤毛其对称轴横向穿过管道，而器官外边缘的静纤毛其轴几乎沿管道纵向排列。瓶状囊斑有前庭上皮的迹象，有高束状的静纤毛，分为静纤毛方向相反的区域以及I型和II型毛细胞。
