Use this URL to cite or link to this record in EThOS: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.344347
Title: The gut of the rainbow trout (Salmo gairdneri) : a gross, histological and ultrastructural study with some aspects of functional significance
Author: Ezeasor, Daniel N.
ISNI:       0000 0001 3455 8609
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1978
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Abstract:
1. The gut of adult rainbow trout, Salmo galrdnerl, was studied by dissection, scanning electron microscopy, light microscopy and transmission electron microscopy 2. The mucosa exhibited the following topographical characteristicss longitudinal ridges in the oesophagus and stomach, villi in the intestine, fine longitudinal ridges in the caeca and annular folds in the rectum, arranged like a stack of caudally-directed funnels starting from the intestino-rectal valve to the vent. Detailed scanning KM studies revealed ta3te pores in the anterior oesophagus and the sculpting of the luminal surface of the surface cells into microridges with complicated patterns. The surfaces of the posterior oesophagus and stomach were demarcated into polygons by rows of 3tubby microvilli - each polygon representing the luminal surface of an epithelial cell. Each rectal fold consisted of a smooth, caudally-directed apex and a base which was supported by perpendicular buttress-like secondary folds. 3. The gut wall consisted of mucosa, submucosa, iausculari3 externa and serosa, showing appropriate regional differences. A muscularis mucosae was present only in the stomach and rectum, a subraucosa only in the oesophagus and stomach, while the muscularis externa consisted of a circular layer of striated muscle in the oesophagus, and two coats of smooth muscle in the remainder of the gut. 4. The oesophageal epithelium showed a progressive posterior reduction in height, ranging from an anterior stratified epithelium to a simple columnar mucous epithelium in the distal third. The epithelium was associated with globular mucous cells and taste buds in the anterior portion, acinar mucous glands in the middle portion, and tubular serous glands in the distal third. 5. Cytological features of the columnar mucous cells lining the surface and pits of the gastric mucosa, oxyntic cells lining the glands and the endocrine cells of the gastric mucosa were studied Microfilaments were prominent in the basal cytoplasm of the surface cells, where they formed annular bands around the convolutions of the basal lamina complex, which Impressed the basal plasma membrane. Release of the mucous vesicles was achieved by exocytosis. The oxyntic cells possessed apical and basal microvillous processes, a well-developed tubulo-vesicular system, zymogen granules, extensive granular endoplasmic reticulum and many large mitochondria. When stimulated by distension of the stomach, the apical cytoplasm was converted into a labyrinth of cytoplasmic processes, while annular lamellae each of which showed a short peripheral linear density, appeared in the basal cytoplasm. The endocrine cells showed such apical modifications as microvilli, cilia, centrioles, small lucent vesicles, microtubules and a reduced glycocalyx covering. Three types were distinguished on the basis of their granular morphology. 6. The absorptive cells of the intestine, caeca and rectum were columnar, bore apical microvilli and possessed lamellar vi structures la their supra-nuclear and basal cytoplasm. Active cells of the intestine contained accumulations of fat particles in the Golgi zone, within the lamellar structures and in the intercellular spaces. Even larger accumulations were observed in the lamellar structures and intercellular spaces of the caecal epithelium. The rectal cells displayed tubular invaginations of the plasma membrane between the microvilli, and many vacuoles in their supra-nuclear cytoplasm. Other cells present included endocrine cells, of which two types were distinguished, goblet cells, pear-shaped cells and intraepithelial leucocytes. 7. The stratum compactum was composed of densely-packed collagenous fibrils arranged in layers. The fibrils within each layer were unidirectional and alternated within adjacent layers, resulting in an overall plywood or orthogonal pattern. Highly active fibroblasts were associated with its internal surface. Granule cells were associated generally with the connective tissue of the gut wall, but the majority were arranged in a definitive layer, the stratum granulesum. Whatever location however, they maintained physical contact with fixed connective tissue cell types, referred to here as 'ensheathing1 cells. Phospholipid, acid mucopolysaccharides and the activities of alkaline phosphatase, acid phosphatase, arylsulphatase, 5-nacleotidase and proxidase were demonstrated in the granule cells. 8. The oesophageal serosa contained vagal nerve trunks, which became incorporated in the myenteric plexus of the stomach. Each trunk was an encapsulated unit containing nerve cell bodies, myelinated and unmyelinated axons and supporting cells. The same elements, with the exception of myelinated axons, constituted the myentaric plexus outside the trunks in the stomach, and in the remaining parts of the gut. The submucous plexus consisted of two tiers in the stomach and only one tier in the post-gastric gut. Contrary to reports in the literature, nerve cell bodies were demonstrated in this plexus. Six types of nerve cell bodies and three groups of axon profiles were distinguished on the basis of their ultrastructure. "En-grappe" and "en-plaque" types of motor end-plates were demonstrated in the muscularis externa of the oesophagus. Amongst the smooth muscle generally, that of the stomach was most sparsely innervated, while that of the rectal muscularis mucosae showed the densest innervation of all, at the same time, containing nerve cell bodies. 9. The co-existence of intraluminal and intracellular digestion of proteins is discussed in relation to diet and the presence of the stratum compactura. The stratum compactum, 'ensheathing' cells and granule cells are hypothesised as constituting part of the bodily defence system. The demonstration of nerve cell bodies in the submucous plexus is 3hown to invalidate the existing schema for telaost gut innervation.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.344347  DOI: Not available
Keywords: Human anatomy & human histology
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