Martynova Marina G, Chaga Oleg Y
Institute of Cytology, Russian Academy of Sciences, 194064 St. Petersburg, Russia.
Department of Cytology and Histology, St. Petersburg University, 199034 St. Petersburg, Russia.
J Morphol. 1997 Oct;234(1):69-77. doi: 10.1002/(SICI)1097-4687(199710)234:1<69::AID-JMOR6>3.0.CO;2-I.
The fine structure of the heart and connective tissue sheath surrounding the stomach of the brachiopod Rhynchonella psittacea has been studied. The stomach wall is lined externally with peritoneal epithelium. Between the bases of the peritoneal epithelial cells and those of the stomach epithelial cells is an extracellular amorphous matrix. The exterior part of the matrix is occupied by smooth muscle cells and the interior part by fibroblasts. The heart wall shows continuity with the peritoneal epithelium covering the stomach wall and consists of three layers: an outer layer of smooth myoepithelial and epithelial cells, an intermediate thick layer of extracellular matrix, and an inner discontinuous layer of fibroblasts. In myoepithelial cells, nucleated heads protruding freely into the coelom and contractile parts embedded in the extracellular matrix can easily be distinguished. These cells contain no sarcoplasmic reticulum or any elements of a T system. The epithelial cells are non-muscular mononucleated cells scattered among the myoepithelial cells and closely associated with these basally. They possess a well-developed rough endoplasmic reticulum. In rare cases, a small amount of myofibrils occurs basally in the epithelial cells. Morphologically the epithelial cells in the myocardium are very similar to the peritoneal epithelial cells covering the stomach wall. Both epithelial and myoepithelial cells are ciliated. No nerve elements have been found in the brachiopod heart. The structure of the brachiopod heart is compared with that of other invertebrates; similarity of cellular composition of the brachiopod heart and stomach cover is considered evidence of origin of the heart cells from the cells of the connective tissue sheath of the stomach. The myogenic role of the peritoneal cells and epithelial cells of the myocardium is suggested. J. Morphol. 234:69-77, 1997. © 1997 Wiley-Liss, Inc.
对鹦鹉贝腕足动物心脏的精细结构以及围绕其胃部的结缔组织鞘进行了研究。胃壁外部衬有腹膜上皮。在腹膜上皮细胞和胃上皮细胞的基部之间是细胞外无定形基质。基质的外部由平滑肌细胞占据，内部由成纤维细胞占据。心脏壁与覆盖胃壁的腹膜上皮相连，由三层组成：外层是光滑的肌上皮细胞和上皮细胞，中间是一层厚厚的细胞外基质，内层是不连续的成纤维细胞层。在肌上皮细胞中，可以很容易地分辨出有核的头部自由伸入体腔，收缩部分嵌入细胞外基质。这些细胞不含肌浆网或任何T系统的成分。上皮细胞是非肌肉单核细胞，散布在肌上皮细胞之间，并在基部与这些细胞紧密相连。它们拥有发达的粗面内质网。在罕见情况下，上皮细胞基部会出现少量肌原纤维。从形态学上看，心肌中的上皮细胞与覆盖胃壁的腹膜上皮细胞非常相似。上皮细胞和肌上皮细胞都有纤毛。在腕足动物心脏中未发现神经成分。将腕足动物心脏的结构与其他无脊椎动物的结构进行了比较；腕足动物心脏和胃覆盖物细胞组成的相似性被认为是心脏细胞起源于胃结缔组织鞘细胞的证据。提出了腹膜细胞和心肌上皮细胞的肌源性作用。《形态学杂志》234:69 - 77，1997年。© 1997威利 - 利斯公司。
