Griffiths M, Slater E
Division of Wildlife and Rangelands Research, CSIRO, Lyneham, Australia.
J Anat. 1988 Feb;156:141-56.
The distribution and amounts of striated muscle within the mammary glands of pouched and pouchless marsupials from Australia and South America are described. Invasions into the mammary secretory parenchyma in pouchless marsupials by swathes of striated muscle from the ilio-marsupialis muscle are massive, in some instances concentrated into discrete muscles, which are inserted on to the bases of the teats; the name retractor mammae is proposed for these muscles. In pouched marsupials striated muscle penetrates the parenchyma, but the distribution is diffuse and the muscle strands are not inserted on to teats except in the instance of the glands of the honey possum Tarsipes rostratus. The young of anaesthetised pouchless marsupials hang down from the teats; as anaesthesia wears off they are hauled up tightly into the mammary area. It is concluded that this is a result of contraction of the retractor mammae muscles and that it is a means of protecting the naked young from injury by rough terrain. The mammary gland musculature in pouched marsupials is considered to be vestigial, but its contraction may have the function of initiating a 'tap-response' contraction of myoepithelium acting synergistically with the 'let-down' hormone mesotocin. Mechanisms of imbibition of milk by marsupial neonates, based on observations that they can suck fluid from non-distortable tubes, are discussed.
本文描述了来自澳大利亚和南美洲的有袋类和无袋类有袋动物乳腺内横纹肌的分布和数量。在无袋类有袋动物中，来自髂袋肌的大片横纹肌侵入乳腺分泌实质的情况很普遍，在某些情况下集中成离散的肌肉，这些肌肉插入乳头基部；为此类肌肉提出了乳头牵缩肌这一名称。在有袋类有袋动物中，横纹肌穿透实质，但分布分散，除了蜜袋鼯（Tarsipes rostratus）的腺体情况外，肌束不插入乳头。麻醉后的无袋类有袋动物幼崽从乳头垂下；随着麻醉效果消退，它们被紧紧拉到乳腺区域。得出的结论是，这是乳头牵缩肌收缩的结果，并且这是保护裸露幼崽免受崎岖地形伤害的一种方式。有袋类有袋动物的乳腺肌肉组织被认为是退化的，但其收缩可能具有引发肌上皮“轻拍反应”收缩的功能，该收缩与“排乳”激素中叶催产素协同作用。基于对有袋类新生儿能够从不可变形的管子中吸取液体的观察，讨论了有袋类新生儿吸乳的机制。
