Surface architecture of the oropharyngeal cavity and the digestive tract of Mulloidichthys flavolineatus from the red sea,Egypt: A scanning electron microscope study

Surface architecture of the buccal cavity and the surface organization of the luminal mucosa of the oesophagus, stomach, and intestine of the carnivorous fish M. flavolineatus from the Red Sea were studied by using SEM. The results revealed that M. flavolineatus has four kinds of teeth; curved-blunt, wedge-shaped, flattened crowns, molariform and papilliform. Three types of taste buds (type I, II and III) were recorded in the oropharyngeal cavity. It was observed that taste buds and teeth are co-located in the pharyngeal region. Characteristic patterns of microridges of the surface cells in the oral cavity and oesophagus were observed. Mucous cells are distributed in the lining of the mouth cavity, oesophagus, stomach, and intestine. Characteristic patterns of mucosal folds throughout the alimentary canal, concerning oesophagus, stomach, and intestine were revealed. Numerous gastric pits, which represents the emergence of the gastric glands, were recorded in the anterior and middle regions of the stomach. Complex patterns of the folds and mucous cells were recorded in the intestinal mucosa. These results were discussed with other teleost fishes.     

日本沼虾消化道形态和组织学特点

应用石蜡切片和扫描电镜技术对日本沼虾消化道进行了研究。结果表明,食道壁向腔内形成四个纵突,食道上皮由单层柱状细胞构成,上皮下的结缔组织中具有放射肌和皮肤腺,环肌层近于连续。食道和胃连结处的管腔背方具食道瓣,胃内具胃磨、滤器和滤沟等结构,胃的组织学结构中除无皮肤腺分布外与食道相似。中肠较长,约占整个消化道的７１７％,具一对中肠前盲囊。中肠上皮细胞大致有两种类型,基膜着色深,环肌层连续,纵肌成束分散排列。后肠为一短管,管腔呈迷路状,其中部为一球形膨大的直肠。后肠的组织学结构与前肠相似。     

Histology and mucin histochemistry of the gastrointestinal tract of the mud loach, in relation to respiration

The gastrointestinal tract of the mud loach Misgurnus mizolepis was divided into an oesophagus, stomach, intestine and rectum which consisted of a mucosa (epithelial layer), lamina propria-submucosa, muscularis and serosa. The intestine and rectum have shorter mucosal folds and a thinner wall than those of the oesophagus and the stomach. Extensive vascular capillary networks were present near the luminal surface of the intestine and the rectum. The diffusion distance between the vascular capillaries and the viscus lumen in the intestinal and rectal mucosal epithelium was 0·7 μm (±0·11). The intestine and rectum of Misgurnus mizolepis probably have a respiratory function to address the deficient oxygen supply within their environment. The epithelial mucous cells contained acidic or a mixture of acidic and neutral mucins, the former being the most common.     

The microscopic anatomy of the oesophagus, stomach and intestine of the channel catfish, Ictalurus punctatus

An anatomical study of the digestive tract of the channel catfish revealed that the oesophageal mucosa was longitudinally folded and that secondary folds were occasionally located on the primary longitudinal folds. The infoldings were more numerous near the stomach. The stratified squamous epithelium covering the folds was made up of a basal layer, large mucous cells and simple squamous cells on the surface. The epithelium on the side of the folds consisted primarily of mucous secreting cells. Taste buds were observed between mucous cells on the apical portion of the oesophageal folds and were more prevalent in the cranial part of the oesophagus. The remaining layers of the oesophagus were: a lamina propria-submucosa, tunica muscularis and adventitia or serosa.
The J-shaped stomach had two regions: a large sac-shaped region containing gastric glands and a smaller, nonglandular pyloric region. The large rugae of the stomach became gradually smaller near the pylorus. There was a well developed pyloric sphincter. The mucosa included a simple columnar epithelium, a lamina propria and adventitia or serosa.
The intestine could be differentiated into a thick ascending segment, a descending segment, a thin convoluted segment and a thicker terminal segment, the rectum. Many mucosal folds containing branched villi characterized the ascending segment of the intestine. The descending and convoluted segments contained fewer folds with shorter and less-branching villi and were smaller in diameter and thinner walled. Descending and convoluted segments were also mildly convoluted and accounted for 80% of the total length of the intestine. An intestinal valve with a sphincter marked the beginning of the rectum. There was an approximately four-fold increase in the thickness of the tunica muscularis of the terminal segment of the intestine.     

Gut morphology and morphometry in the epauletted Wahlberg's fruit bat (Epomophorus wahlbergi, Sundevall, 1846)

The morphological adaptations of the fruit bat small intestine to which the high functional efficiency could be related and the possible landmarks delineating the various parts of the gut were examined. The stomach was the carnivorous type with large rugae spanning the entire luminal aspect down to the pyloric sphincter, which was reflected internally as a prominent fold. Externally, the intestine was a continuous tube uninterrupted by any structures. The cranial fifth of the small gut had long, branching and anastomosing villi, which caudally turned to finger-like discrete structures that became rather short and stumpy and diminished at the beginning of the colon. The colon had longitudinal folds that were macroscopically discernible from the mucosal aspect of the opened intestine and that continued into the rectum. The small gut formed 94% of the whole intestinal length, the colon and the rectum taking 4 and 2%, respectively. Ultrastructurally, the enterocyte showed a prominent brush border and the lateral membranes were modified into numerous tortuous interdigitating processes. Adjacent enterocytes were joined by these processes through desmosomes. The processes also participated in pinocytotic fluid uptake from the intercellular spaces with resultant numerous intracellular vacuoles of varied sizes. Solutes absorbed into the cells were probably first passed into the intercellular compartment to create a concentration gradient thus enhancing further absorption into the cell. We conclude that the uniquely elaborate ultrastructure of the enteric epithelium coupled with the vast microvillous surface areas reported elsewhere are partly responsible for the very high absorption rates reported in the fruit bat small intestine.     

The digestive tract of the amberjack Seriola dumerili, Risso: a light and scanning electron microscope study

The histology of the digestive tract of the amberjack ( Seriola dumerili , Risso) was studied using light and scanning electron microscopy. The anterior oesophagus mucosa displays primary and secondary folds lined with a stratified squamous epithelium with fingerprint-like microridges which is substituted, on the top of the oesogaster folds, by a simple columnar epithelium with short microvilli. Only primary folds are present in the stomach. The anterior portion is rich in simple tubular glands, whereas the oesogaster and the pyloric region are devoid of them. Pyloric caeca and anterior and middle intestine mucosa display the same pattern of folding. The dominant cell type is the enterocyte, which exhibits larger and thinner microvilli in the caeca than in the intestine. The columnar epithelium of the rectum is replaced, in the anal sphincter, by a stratified flattened epithelium. Goblet cells are numerous throughout the whole length of the tract with the exception of the initial part of the oesophagus, the oesogaster, the stomach and the anal sphincter. Mucosubstances have been shown to vary in the different regions of the gut: acid mucines are found in the oesophagus, pyloric stomach, caeca, intestine and rectum, whereas neutral mucosubstances dominate in the anterior portion of the stomach. The muscularis is well developed throughout the length of the tract: two layers of striated muscle at the oesophageal level; two layers of smooth muscle in the stomach wall and three at the intestinal level.     

Immunohistochemical analysis of connexin26 and 43 expression in the mouse alimentary tract

The spatial pattern of connexins26 (Cx26) and 43 (Cx43) expressions were investigated in the mouse digestive tract by immunocytochemistry. High levels of connexin43 in the epithelium of the oesophagus, non-glandular part of the stomach, and the circular layer of duodenal and ilea muscularis externa were detected. Cx26 was expressed in stratum granulosum of oesophagal folds and in the non-glandular part of the stomach. A low level of immunoreactivity of Cx43 was observed in the circular, and very low in the longitudinal layer of the muscularis externa in the stomach and colon. No immunoreactivity for Cx26 and Cx43 was found in the entire muscularis externa of the oesophagus or in the longitudinal muscle layers of the duodenum and ileum.     

Ultrastructural localization of the circulating cathodic antigen in the digestive tract of various life-cycle stages of Schistosoma mansoni

In the present study the ultrastructural localization of the schistosome-derived circulating cathodic antigen (CCA) within the digestive tract of various life-cycle stages of the blood fluke Schistosoma mansoni has been determined. Use was made of CCA-specific monoclonal antibodies in a two-step gold-labeling procedure. The following results were obtained: In cercariae gold label was found in the cytoplasm and in the luminal surface coat of the gut epithelium. The oesophagus of this life-cycle stage of the parasite showed minimal CCA reactivity, as gold label was limited to the luminal surface coat, locating proximally to the gut. In 3 1/2-week-old worms and in adult male and female worms CCA was demonstrable in the Golgi apparatus, in cytoplasmic vesicles and in the luminal surface coat; in the caudal quarter of the gut of adult worms CCA was also present in lysosome-like bodies. The oesophagus of these worm preparations did not show any CCA reactivity. In miracidia CCA was not present.     

Three-dimensional development of luminal projections and junctional complexes in the developing central nervous system blood vessels of the rat

Summary The luminal surface features and Junctional complexes from developing blood vessels in the rat central nervous system have been studied by high-voltage electron microscopy and scanning electron microscopy. Developing blood vessels exhibit three types of luminal projections; marginal folds or ridges at Junctional complexes, ridges not at Junctional complexes and microvilli. Both types of ridges are associated with troughs or depressions in the luminal surface of the endothelial cell. Those ridges not associated with Junctional complexes take part in the production of enclosed tunnels in the endothelial cell cytoplasm. Fusion of the external leaflets of Junctional complexes between adjacent endothelial cells occurred, initially, near the luminal surface of the blood vessel with other small fusion sites forming in the direction of the basal lamina secondarily. Further fusion activity to produce the zonula occludens type junction appeared to spread outwards from the smaller fusion sites.Supported in part by a NIH HVEM Travel Grant and the Medical College of Georgia     

A study of the histology and morphology of the digestive tract of the common eel (Anguilla anguilla)

The anatomy and morphology of the digestive tract of the eel was examined using light and scanning electron microscopy. The oeosphagus showed complex longitudinal folding; stratified epithelium, columnar epithelium and goblet cells striated muscle fibres formed the thick muscular coat. The pneumatic duct entered the oesophagus anterior to the oesophagastric junction. The Y shaped stomach showed large well developed folds which decreased in size and number towards the pyloric sphincter. Columnar epithelium and gastric gland cells were present, the latter being absent from the pyloric region.
The intestine had a heavily thickened anterior region, signs of convulation were noted prior to the ileorectal valve. Intestinal folding showed a complex reticulate pattern with columnar epithelium and goblet cells present. The mucopolysaccharides were studied in the goblet and columnar cells throughout the regions of the gut. Lymphocytes and eosinophilic type cells were found in the connective tissue of the mucosa throughout the gut. The pancreas was a compact organ with few Islets of Langerhans, beta cells were peripherally situated and alpha cells centrally. The unilobular liver acted as a storage organ for oil and glycogen.     

Morphological and histochemical features of the digestive tract of Leiarius marmoratus (Gill, 1870)

Leiarius marmoratus, a freshwater catfish from Pimelodidae family, shows great biological and commercial relevance because of its geographic distribution and adaptation to fish-farm. The knowledge of the morphological characteristics of the digestive tract is fundamental to the understanding of fish physiology and nutrition, which helps in the planning of diets to provide better management and success in fish farming. Thus, this work described the morphology and histochemistry of the digestive tract of L. marmoratus adults. After euthanasia, the animals were dissected for analysis of the digestive tract. The oesophagus is a short and distensive organ with longitudinal folds that allow the passage of large food, e.g., other fishes. Oesophageal mucosa layer shows a stratified epithelium with goblet cells and club cells. The secretion of goblet cells is composed of neutral and acidic mucins that are anchored in the epithelium luminal face by epithelial cells fingerprint-like microridges, lubricating the surface to facilitate the food sliding. Club cells have protein secretion that can be involved in alarm signals when epithelium is damaged and in immunological defence. The saccular stomach is highly distensible to store large food. Gastric mucosa layer is composed of epithelial cells with intense secretion of neutral mucin to protect against self-digestion of gastric juice. Cardiac and fundic regions of stomach show well-developed gastric glands composed of oxynticopeptic cells. These cells have numerous mitochondria, highlighting their intense activity in the synthesis of acid and enzymes. The intestine is divided into three regions: anterior, middle and posterior. Although it is a short tube, intestine shows longitudinal folds and microvilli of enterocytes to increase the contact surface. These folds are higher in the anterior region of the intestine, highlighting their function in digestion and absorption. Intestinal goblet cells have acidic and neutral mucins that lubricate the epithelium and aid in digestive processes. These cells increase in number towards aboral, and they are related to the protection and lubrication to expulsion of faecal bolus.     

Morphological and histochemical characterisation of the mucosa of the digestive tract in matrinxã Brycon amazonicus (Teleostei: Characiformes)

This study describes anatomical, histological and histochemical features of the digestive tract mucosal layer of the matrinxã Brycon amazonicus, an omnivorous freshwater fish endemic from the Amazon basin. This species presents short thick oesophagus with longitudinal folds, that allow the passage of large food items. The mucosa is lined with a stratified secretory epithelium rich in goblet cells that secrete neutral and acid mucins. The two mucin types provide different viscosity in anterior and posterior oesophagus related to the protective and lubricant functions, respectively. The stomach is a highly distensible Y-shaped saccular organ. Here, it is proposed that this anatomical shape plays an essential role in food storage when food availability is abundant. The stomach mucosa is composed of epithelial cells with intense neutral mucin secretion to protects against gastric juice. The intestine is slightly coiled and presents internally a complex pattern of transversal folds that increases the absorption surface and the retention time of food. Goblet cells in the intestine secrete acid and neutral mucins that lubricate the epithelium and aid in the digestive processes. In the rectum, an increase in goblet cells population occurs that may be related to better lubrication.     

Structure of the gut of the racer goby Neogobius gymnotrachelus (Kessler, 1857)

The morphological and histological features of the gut of juvenile racer goby Neogobius gymnotrachelus [range of body mass 0·2–0·9 g and standard length ( L _S) 20·0–38·8 mm] were examined in fish collected from the Włocławek Reservoir on the Vistula River, Poland. Evidence is provided of the stomachless nature of the gut of the racer goby. The intestine of the juveniles lacks the intestinal bulb. A particular feature of the racer goby gut is the secretory oesogaster (the transitional region where the secretory oesophagus merges into the intestine) with multicellular alveolar glands that secrete via a common duct to the surface between the mucosal folds. The cells in the secretory oesogaster alveolar glands are periodic-acid-Schiff (PAS) positive indicating the presence of neutral mucopolysaccharides. It is hypothesized that the secretory oesogaster is evidence of the loss of the functional stomach in this species. There are two sphincters: the oesogaster–intestinal and the intestinal–rectal in the racer goby gut. It can be concluded that the oesogaster–intestinal sphincter is functionally related to the gastro-intestinal sphincter described in many fish species having a stomach. Enterocytes with a distinct brush border and only a few goblet cells are observed in the epithelium along the whole intestine. The existence of vacuoles in the supranuclear region of the rectal enterocytes is also confirmed.     

马铁菊头蝠消化系统的组织学观察

应用石蜡常规切片、HE染色,对马铁菊头蝠消化系统各器官的组织结构进行了观察.结果 表明:食管粘膜上皮为复层扁平上皮,轻微角质化,前、中、后段的上皮结构没有显著差异,食管腺在前段较多,中、后段较少.胃固有层含有大量的管状腺.小肠粘膜表面有许多环形皱襞,在十二指肠上段粘膜下层分布有十二指肠腺.大肠粘膜表面光滑,无绒毛,在粘膜下层的结缔组织中有小动脉、静脉和淋巴管.肝内结缔组织多,肝小叶分界较明显,肝血窦发达.胰的小叶间分界不明显.     

龟足消化系统形态和组织学特点

应用光学显微镜观察龟足（Capitulum mitella）消化系统的形态和组织结构。龟足的消化系统包括消化腺和消化道。消化腺一对,呈长囊状,含有分泌细胞（B细胞）、吸收细胞（R细胞）、储存细胞（F细胞）和胚细胞（E细胞）4种类型细胞。消化道呈U型,由口、食道、胃、肠、直肠和肛门组成,各部分的结构由内到外可分为黏膜层、黏膜下层、肌层和外膜4层。口器为咀嚼型,包括一片上唇、一对触须、一对大颚以及两对小颚。食道细短,具几丁质层但无基膜,管壁向腔内突起形成明显的纵褶突;食道前段的环肌特别发达,同时独有放射肌。胃略呈球袋状,肠较长;胃和肠的组织结构相似,没有几丁质层,上皮细胞都有发达的微绒毛。直肠细长,外膜分布有16组纵肌;直肠前段的组织结构与胃、肠相似,而直肠后段有几丁质层覆盖,黏膜层、黏膜下层、肌层和外膜渐退化,16组纵肌渐发达。肛门16组更加发达的纵肌挤入上皮细胞下方,在外膜外另出现一层明显的环肌。龟足消化道各部分的组织结构差异明显,反映了它们功能的差异。     

The bovine tubouterine junction: general organization and surface morphology

The bovine tubouterine junction is composed of three parts (terminal tubal segment, transition region proper, uterine apex) and follows a sigmoidal course displaying a tubal and an uterine curvature. In the terminal tubal segment, 4–8 primary longitudinal folds and a system of lower secondary folds, ridges and chords project into the centrally located lumen. The transition region proper possesses a slit-like lumen because of the existence of a thick mucosal pad containing the first uterine glands. The longitudinal primary folds of the tube broaden, flatten and start to diverge when they reach the transition region proper. The mucosal pad and broadened folds are heavily vascularized. A system of lateral outpocketings with blind ends pointing in an ampullary direction develops between the primary and secondary folds, the ridges and chords of the terminal tubal segment and transition region proper. From the bottom of these outpocketings, short tubulo-alveolar crypts originate. The mucosa of the uterine apex forms low transversal ridges. The musculature of the bovine tubouterine junction is divided into a continuous circular or spiral intermediate layer, flanked by inner and outer longitudinal layers. The outer longitudinal layer is incomplete in the terminal tubal segment but increases in thickness to form a continuous stratum in the uterine apex. An inner longitudinal layer occurs only in the terminal tubal segment where it is best developed in the bases of the primary longitudinal folds. The simple columnar surface epithelium of the tubouterine junction contains ciliated and non-ciliated cells. The former undergo cyclical changes, and increase during estrus and postestrus. During proestrus, groups of non-ciliated cells display bulbous apical protrusions. During proestrus and estrus, circumscribed epithelial lesions expose the underlying basal lamina.     

Ultrastructure of the foregut and associated glands of Calicotyle kröyeri (Monogenea: Monopisthocotylea)

The mouth, pharynx and oesophagus of Calicotyle are lined by syncytial epithelia, and there are numerous unicellular glands associated with the oesophagus. An infolding of unmodified external tegument lines the mouth cavity and is connected by discrete cytoplasmic processes to subjacent perikarya. It contains two types of secretory body and its luminal surface is invested with a finely filamentous coating. The pharynx and oesophagus are lined by irregularly-folded epithelia that are interconnected by a septate desmosome. Membranous inclusions distinguish the pharynx epithelium and there is a well developed basal lamina for insertion of the pharyngeal muscles. The oesophagus epithelium is perforated by the openings of the oesophageal glands. These lie in the surrounding parenchyma and produce a dense, membrane-bound secretion which is conveyed by duct-like extensions of the glands to the oesophagus lumen. The ducts are supported in places by microtubules and are anchored to the oesophageal epithelium by septate desmosomes. A septate desmosome also marks the junction between the epithelium and the gut caeca.     

The anatomy and histology of the alimentary tract of the carnivorous fish the pike Esox lucius L.

The alimentary tract of the pike is described, relating its feeding habits to its intestinal gut histology. It is a carnivorous species having a short oesophagus, pouch-like stomach and a short intestine with two convolutions. Stratified epithelium with columnar cells and many goblet cells are present in the oesophagus, columnar epithelial cells only in the stomach, and both cell types in the intestine.
Eosinophils in the mucosa of the oesophagus originate from connective tissue cells and lymphocytes and neutrophils are present. The lamina propria is composed of a stratum granulosum, stratum compactum, blood vessels and loose areolar tissue. The stratum compactum is a strengthening substance, composed of collagen, characteristic of carnivorous teleosts. The circular and longitudinal muscle layers and serosa are similar to those of other carnivorous teleosts.
The pancreas and liver are briefly described, the pancreas being the unusual compact type not often found in teleosts. The B cells are seen in the periphery and a cells in the centre of the islets. The liver is a unilobular organ, having oil storage as a major function.
The distribution of goblet cell mucin is given, differentiating it into neutral and acid mucosubstances. Nine levels of alimentary tract were examined in the mucin distribution study. The functions of mucin in the pike are digestion, absorption, protection and lubrication.     

Gross anatomical and histomorphological features of the Acanthopagrus schlegelii digestive tract (Bleeker 1854) Perciformes,Sparidae

Acanthopagrus schlegelii is an autochthonous teleost species concerning the remarkable economic importance and prevalent fish cultivated in China as well as in different nations of South-East Asia. Little is known about the digestive tract (DT) morphology of A. schlegelii. Therefore, anatomical and histomorphological aspects of A. schlegelii DT were examined by light and scanning electron microscope (SEM). Anatomically, DT of A. schlegelii was mainly formed of oesophagus, well-developed stomach and fingers like pyloric caeca (four in number), intestinal regions and rectum. Histomorphologically, oesophagus occurred as a shorter tube-like organ presenting a longitudinal folded mucosa that connects oropharynx cavity to stomach. Stomach was a muscular thick-wall organ that included three regions, thickly longitudinal folds were observed in the first (cardiac) and last (pyloric) regions, whereas the second (fundic) region showed folds in different directions. Long villi were observed within pyloric caeca and anterior intestine. Tunica muscularis appeared narrow in the anterior intestine, whereas thicker in the posterior part of the intestine. Collectively, anatomical and histomorphological aspects of A. schlegelii DT are consistent with the carnivorous habit of this species. These data could be a potential source to modify better methods of nutrition and identify the DT pathogenic conditions in farming of this fish.