Scanning electron microscopy of the developing alimentary canal in the chick

Abstract

Fresh pullet eggs (White Leghorn strain) were incubated from 11 to 21 days. Embryos were killed by decapitation and portions of the esophagus, crop, proventriculus, gizzard, small intestine, caecum and rectum were dissected and removed rapidly. The inner lining of the gut was exposed by using small needles to pin the cut edges of the tube to a wax plate immersed in Hank's fixative modified with aldehydes (Litke and Low, '77). Preparation for scanning electron microscopy (SEM) was routine.Esophageal cilia appeared in tufts along with microvilli and microplicae. These were more frequent a t the lower end of the esophagus. Developing cilia were present. In the 12-day proventriculus, structures resembling macrovilli were predominant. These disappeared by the seventeenth day, when aggregates of rounded cells covered with microvilli appeared. The gizzard acquired a prominent rounded cellular appearance with microvilli a t 17 days. These cells increasingly elongated and flattened out towards hatching (21 days). Observations of the duodenum confirmed those made by Grey ('72). A hexagonal pattern of cells was also observed. The ridges of the ileal portion of the small intestine were larger and fuller than in the duodenum. Formation of rectal villi was not as well organized as in the small intestine. Villi could be seen scattered a t random a t 12 days. By 17 days, definitive ridges were seen. The villi in the cloaca1 region of the rectal area were extremely long and elaborate, as previously reported by Zeitschmann ('02, cited by Calhoun, '57). Our observations show that the mucosal surfaces become highly specialized in different parts of the tract during development. Marked changes in geometric form occur during development.

Development of esophageal epithelium in the fetal and neonatal mouse

“…In chick, ciliated cells first appear in the lower esophagus of the 13 day embryo (Ivey and Edgar, 1952). Using SEM, Lim and Low (1977) observed that ciliated cells were more profusely distributed at the lower end of the chick esophagus, in accordance with the observations of Ivey and Edgar (1952). In mouse, very few ciliated cells are seen at 15 days of gestation, but they are present in all regions of the esophagus.…”

“…In the chick, ciliation of the esophageal epithelium has also been reported (Ivey and Edgar, 1952;Van Alten and Fennell, 1957;Lim and Low, 1977). The presence of ciliated cells in the fetal mouse esophageal epithelium is reported here for the first time.…”

“…Using the same technique, Lim and Low (1977) described the presence of short, stubby microvilli as well as micropli- cae on the apical cell surfaces in the chick embryo. In the mouse fetus, the cell surface of nonciliated cells is covered with short microvilli only.…”

Development of longitudinal mucosal folds in the intestine of the anadromous sea lamprey, Petromyzon marinus L., during metamorphosis

“…The developing longitudinal folds of the lamprey anterior intestine most closely resemble the previllous ridges in the developing avian duodenum (Tsai and Overton 1976;Lim and Low 1977) in that both follow a zigzag course. The primary difference is that in lampreys the pattern is irregular and more widely spaced such that the concavities and convexities of adjacent folds do not always meet as they do in the duodenum of a 15-day-old chick embryo (Lim and Low 1977).…”

Histogenesis of the mouse jejunal mucosa, with special reference to proliferative cells and absorptive cells.

“…The end of the rough endoplasmic reticulum is continuous to the smooth elements (arrows) on day E17. x 15,000 chick duodenum (COULOMBRE and COULOMBRE, 1958;GREY, 1972;BURGESS, 1975;LIM and Low, 1977) and the rat duodenum (KAMMERAAD, 1942;MATHAN et al, 1976;NAKAMURA and KoMURO, 1983). In the chick, the authors agreed in that villous primordia started as parallel previllous ridges, which folded to a regular zigzag pattern and then separated into individual villi, and these events proceeded synchronously throughout the mucosa.…”