Block10-2/Fig 4. 93W4558, Recto-anal junction (ls) H&E.

block10-2_11.jpg - Fig 4. 93W4558, Recto-anal junction (ls) H&E.A view of the recto-anal junction is shown at Fig 4a. Mucosacharacteristic of the anal canal is seen on the lower left of themicrograph. This region has the intestinal glands same as thosepresent in the colon. At the level of the anal canal, themuscularis mucosa disappears, and the circular layer of themuscularis externa (smooth muscle) thickens to become theinternal anal sphincter (I). The external anal sphincter (E) isformed by the striated muscles of the pelvic floor. The rectangleof Fig 4a is examined at higher magnification in Fig 4b.Fig 4b shows the junction between the simple columnar and thestratified epithelium (marked with the arrowhead). The simplecolumnar epithelium of the anal canal contains numerous gobletcells (G). As in the mucosa of colon, the epithelium iscontinuous with the epithelium of the intestinal gland (IG).These glands continue to about the same point as themuscularis mucosa. Characteristically, the lamina propria (L)contains large numbers of lymphocytes.

Fig 4. 93W4558, Recto-anal junction (ls) H&E. A view of the recto-anal junction is shown at Fig 4a. Mucosa characteristic of the anal canal is seen on the lower left of the micrograph. This region has the intestinal glands same as those present in the colon. At the level of the anal canal, the muscularis mucosa disappears, and the circular layer of the muscularis externa (smooth muscle) thickens to become the internal anal sphincter (I). The external anal sphincter (E) is formed by the striated muscles of the pelvic floor. The rectangle of Fig 4a is examined at higher magnification in Fig 4b. Fig 4b shows the junction between the simple columnar and the stratified epithelium (marked with the arrowhead). The simple columnar epithelium of the anal canal contains numerous goblet cells (G). As in the mucosa of colon, the epithelium is continuous with the epithelium of the intestinal gland (IG). These glands continue to about the same point as the muscularis mucosa. Characteristically, the lamina propria (L) contains large numbers of lymphocytes.

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