Mahdi A H, McLelland J
Department of Preclinical Veterinary Sciences, University of Edinburgh, Scotland.
J Anat. 1988 Dec;161:133-42.
The arrangement of the muscle at the ileo-caeco-rectal junction of the domestic duck (Anas platyrhynchos) was studied using light microscopy, three-dimensional reconstruction models and scanning and transmission electron microscopy. The junction consists of a papilla-like protrusion of the ileum into the rectum, the 'ileal papilla', lateral to which are the openings of the large right and left caeca. The ileal papilla consists entirely of circular muscle which is not divided into an inner electron-dense portion and an outer electron-lucent portion as is the rest of the ileum. The longitudinal muscle layer does not enter the ileal papilla. The circular muscle at the junction forms three thickenings or sphincters which are continuous with one another: an ileal sphincter in the ileal papilla, and right and left caecal sphincters around the orifices of the caeca. The majority of nerve bundles are found in the circular muscle layer and consist of axons with small granular vesicles, axons with small agranular vesicles and axons with many large granular vesicles. The density of innervation, including the total number of axon profiles and the number of vesiculated axon profiles, is significantly higher in the circular muscle of the sphincters than in the ileum, caecum and rectum 5 mm from the junction.
利用光学显微镜、三维重建模型以及扫描和透射电子显微镜，对家鸭（绿头鸭）回肠 - 盲肠 - 直肠交界处的肌肉排列进行了研究。该交界处由回肠向直肠突出形成的乳头状突起“回肠乳头”组成，在其外侧是左右大盲肠的开口。回肠乳头完全由环形肌构成，不像回肠其他部分那样分为内侧电子致密部分和外侧电子透亮部分。纵肌层不进入回肠乳头。交界处的环形肌形成三个彼此连续的增厚部分或括约肌：回肠乳头内的回肠括约肌，以及围绕盲肠开口的左右盲肠括约肌。大多数神经束位于环形肌层，由带有小颗粒囊泡的轴突、带有小无颗粒囊泡的轴突和带有许多大颗粒囊泡的轴突组成。与距交界处5毫米处的回肠、盲肠和直肠相比，括约肌环形肌中的神经支配密度（包括轴突轮廓总数和有囊泡轴突轮廓数）显著更高。
