In present investigation, the muscular covering of canine’s ileum was studied by light and electron microscopes. Five healthy female dogs under general anesthesia and sterile conditions were laparatomized and distal portion of ileum was exposed. From each dog, two samples were obtained for light and electron microscopic studies. Firts sample was fixed in formalin saline, stained by hematoxyline and eosine method, and examined descriptively at light microscopic level. Second sample was prepared for transmission electron microscopic (TEM) study, therefore semithin and ultrathin sections obtained and stained. Semithin sections were examined by light microscope quantitavely and ultrathin sections were observed by low and high magnification of TEM. Light microscopic studies showed routine description of longitudinal and circular layers of muscular covering of ileum. TEM studies showed circular layer composed of a thick portion which located laterally and a thin portion which located internally. Depth of the thick portion was from 21.7+4.4prn to 80+5.7pm and deth of the thin portion was from 1.6+0/46prn to 6.2+2pm. In the thin portion, cell were smaller, spaces between them were narrow and
one gap junction between smooth muscle cells was observed. Circular layer of ileum had two distinct portions and the existence of gap junction between smooth muscle cell of them could be the reason of individual functions of them.
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