Histo Lab- Digestive System (Aughey)

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Tongue (cat). (1) Stratified squamous non-keratinized epithelium. (2) Vascular lamina propria with small projections. (3) Striated muscle fibres. H & E. ×25.

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Tongue (dog). (1) Stratified squamous keratinized epithelium on the dorsum of the tongue. (2) Lamina propria. (3) Striated muscle fibres cut in longitudinal section and (4) in transverse section. (5) Mixed salivary gland. Masson’s trichrome. ×25.

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Tongue (cow). (1) Filiform papilla. (2) Lenticular papilla. Masson’s trichrome. ×41.5.

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Circumvallate papilla. Tongue (cow). (1) Stratified squamous epithelium. (2) Vallum. (3) Taste buds. (4) Lamina propria. (5) Striated muscle. (6) Mixed salivary gland. Gomori’s trichrome. ×100.

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Tongue (cow). (1) Taste buds in the stratified squamous epithelium of the lateral wall of the papilla. The taste pore is arrowed. (2) Connective tissue lamina propria. Masson’s trichrome. ×250.

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Foliate papilla. Tongue (rabbit). This papilla appears as a row of fungiform papillae. The taste buds are arranged along the lateral walls. H & E. ×62.5.

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Taste bud. Tongue (cow). (1) Taste pore. (2) Taste receptor and sustentacular cells. H & E. ×62.5.

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Mixed salivary gland (cow). The main mass of tissue is secretory units of seromucous acini. (1) Interlobular connective tissue with (2) blood vessels. (3) Interlobular ducts. H&E. ×125.

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Mixed salivary gland (cow). Mixed seromucous acinus with (1) pale staining mucous cells and (2) darkly stained serous cells. Masson’s trichrome. ×125.

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Mixed salivary gland (dog). (1) Interlobular duct lined by a stratified columnar epithelium. (2) Connective tissue stroma. (3) Parasympathetic ganglion. (4) Seromucous acini. H & E. ×125.

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Mixed salivary gland (dog). (1) Pale staining triangular mucous cells with a basal nucleus. (2) Deeply staining serous cells with a round nucleus. Gomori’s trichrome. ×125.

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Hard palate (ox). (1) Stratified squamous epithelium. (2) Lamina propria. (3) Mucus-secreting glands in the lamina propria. H & E. ×125.

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Soft palate (ox). (1) Respiratory epithelium. (2) Lymph nodule. (3) Bone. H & E. ×62.5.

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Developing tooth (cat embryo). (1) Oral epithelium. (2) Enamel organ surrounded by mesoderm. H & E. ×12.5.

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Developing tooth (cat embryo). (1) Mesenchymal papilla with a layer of odontoblasts (arrowed). (2) Inner enamel epithelium, continuous with (3) the outer enamel epithelium. (4) Stellate reticulum. H & E. ×62.5.

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Developing tooth (cat embryo). (1) Mesenchymal dental papilla. (2) Ameloblasts in the inner enamel epithelium. (3) Outer enamel epithelium. (4) Stellate reticulum. H & E. ×62.5.

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Developing tooth (cat embryo). (1) Mesenchymal dental papilla lined by odontoblasts. (2) Inner enamel epithelium, ameloblasts, turns to become (3) outer enamel epithelium at the point of root development (arrowed). H & E. ×125.

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Developing tooth (cat). The ameloblasts are tall columnar cells with a basal nucleus (arrowed). H&E. ×125

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Oropharynx. (1) Stratified squamous epithelium. (2) Mucus secreting glands open onto the surface (arrowed). H & E. ×62.5.

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Oesophagus (cat). (1) Stratified squamous keratinized epithelium. (2) Lamina propria. (3) LS vein. (4) Inner layer of circular smooth muscle. (5) Outer layer of longitudinal smooth muscle. H & E. LP.

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Oesophagus (dog). (1) Stratified squamous epithelium. (2) Mucus-secreting glands in the lamina propria. (3) Inner layer of circular skeletal muscle. (4) Outer layer of longitudinal skeletal muscle. H & E. ×12.5.

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Oesophagus (cat). (1) Stratified squamous epithelium. (2) Lamina propria. (3) Muscularis mucosae. (4) Submucosal mucous glands. (5) Muscularis externa. Masson’s trichrome. ×12.5.

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Oesophagus (dog). (1) Stratified squamous epithelium. (2) Lamina propria. (3) Muscularis mucosae. (4) Submucosal mucous glands. (5) Striated muscle of the muscularis externa. H & E. ×62.5.

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Oesophageal/stomach junction (horse). The epithelium changes abruptly from stratified squamous to simple columnar at the junction (arrowed). H & E. ×62.5.

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Oesophageal/stomach junction (horse). The epithelium changes abruptly from stratified squamous to simple columnar at the junction (arrowed). H & E. ×100.

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1.__ 2.__

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Rumen (sheep). (1) Stratified squamous epithelium lines the rumen. (2) Lamina propria. Masson’s trichrome.×12.5.

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Rumen (goat). The lining epithelium is stratified squamous. The lamina propria is loose connective tissue, stained green. Gomori’s trichrome. ×12.5.

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Reticular groove (goat). The mucosa is folded; this allows stretching. The lining epithelium is stratified squamous. H & E. ×12.5.

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Omasum (sheep). The muscularis mucosae is present in the long omasal folds (arrowed). H & E. ×12.5.

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Abomasum. Fundic region (goat). (1) Mucosa. (2) Muscularis mucosae. (3) Submucosa. (4) Muscularis externa. Masson’s trichrome. ×25.

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Abomasum. Pyloric region (goat). (1) The lining epithelium is simple columnar and mucus secreting. (2) Simple tubular mucus-secreting glands. (3) Muscularis mucosae. (4) Submucosa. H&E. ×62.5.

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Stomach (horse). (1) Simple columnar mucus-secreting epithelium. (2) Gastric pits. H & E. ×62.5.

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Cardiac glands. Stomach (horse). (1) Parietal cell. (2) Zymogen cell. (3) Lamina propria. H & E. ×125.

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Fundic glands. Stomach (horse). Simple mucus-secreting epithelium extends into the gastric pits (arrowed). (1) Parietal cell. (2) Zymogen cell. H & E. ×250.

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Fundic glands. Stomach (dog). Simple columnar mucus-secreting epithelium extends into the gastric pits (arrowed). (1) Parietal cell. (2) Zymogen cell. (3) Muscularis mucosae. (4) Submucosa. H & E. ×125.

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Fundic glands. Stomach (dog). Simple columnar mucus-secreting epithelium extends into the gastric pits (arrowed). (1) Parietal cell. (2) Zymogen cell. H & E. ×160.

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Fundic gland. Stomach (cat). (1) Parietal cell. (2) Zymogen cell. H & E. ×250.

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Pyloric glands. Stomach (pig). Simple columnar mucus-secreting epithelium extends into the gastric pits (arrowed). (1) Simple tubular mucus-secreting glands. (2) Muscularis mucosae. (3) Submucosa. H & E. ×25.

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Pyloric glands. Stomach (dog). Simple columnar mucus-secreting epithelium extends into the gastric pits (arrowed). Simple columnar epithelium lines the gland tubule seen here cut in transverse section. H & E. ×100.

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Myenteric nerve plexus. Stomach (horse). Parasympathetic neuron cell bodies (arrowed) lie in the connective tissue between the smooth muscle layers. H&E. ×125.

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Duodenum (dog). (1) Mucosa. (2) Submucosa. (3) Muscularis externa. (4) Serosa. H & E. ×25.

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Duodenal villi (dog). The finger-like villi project into the lumen of the duodenum. Scanning electron micrograph.×100.

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Duodenum (dog). (1) Villus covered by simple columnar epithelium. (2) Lamina propria forms the core of the villus; the contractile crypts are arrowed. (3) Mucosal glands. H & E. ×62.5.

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Duodenum (horse). (1) Goblet cells in the epithelium are stained deep pink. (2) Lamina propria. Haematoxylin/PAS. ×125.

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Duodenum (horse). (1) Simple columnar epithelium with goblet cells. (2) Lamina propria with smooth muscle fibres (arrowed). (3) Contractile crypts. H & E. ×250.

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Duodenum (dog). (1) Mucosal glands. (2) Muscularis mucosae. (3) Submucosal glands. H & E. ×160.

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Duodenum (dog). The lamina propria is filled with lymphatic tissue and lymphocytes are seen migrating through the epithelium (a Peyer’s patch). H.& E. ×12.5.

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Globular leucocyte (horse). The globular leucocyte (function unknown) is in the epithelium of the intestinal gland. A plasma cell is present in the lamina propria (arrowed). H & E. ×500.

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Enteroendocrine argentaffin cell (cat). Argentaffin cell stains black in the intestinal gland epithelium. Methanamine silver/safranin. ×500.

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Colon (horse). (1) Mucosa. (2) Muscularis mucosae. (3) Submucosa. H & E. ×9.7.

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Colon (horse). (1) Simple columnar epithelium with goblet cells. (2) Intestinal mucosal glands. H & E. ×125.

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Anal sac (dog). (1) Stratified squamous keratinized epithelium lines the sac. (2) Tubuloalveolar glands in the lamina propria. H & E. ×12.5.

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Tongue of a poison-arrow frog (Dendrobatesspp.). The dorsal lingual surface (1) is covered by an unusual and complex epithelium composed of small, dark-staining cuboidal cells and acini of sticky mucin-secreting columnar cells that maintain a coating of adhesive mucus. The muscle fibres (2) are primarily arranged in a longitudinal direction and are attached at the front of the mandible. This facilitates the tongue being rapidly protruded and retracted in order to catch small invertebrates. H & E. ×12.5.

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The tongue of some lizards overlies a sublingual salivary gland (1), as is illustrated by this longitudinal section of the tongue of a small skink (Scincella lateralis). The dorsal surface is covered by a non-keratinized stratified squamous epithelium (2) in which cup-shaped taste receptors are embedded. Some lizards (for example, many iguanines) possess tongues with a terminal tip composed of papillary projections that are kept moist and sticky with mucus secreted by goblet cells and several salivary glands. H & E. ×62.5.

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The fangs of venomous snakes are continually being renewed. Illustrated are several teeth primordia of a juvenile rattlesnake (Crotalus spp.), forming modified fangs with a central enamel-lined channel through which venom is conducted. H & E. ×12.5.

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Some non-venomous snakes possess modified (Duvernoy’s) maxillary and premaxillary salivary glands connected to short ducts that empty into the oral cavity. Current studies indicate that the secretions from some of these glands manifest venom-like bioactivity on the lower vertebrate prey of these snakes. Also, mild clinical envenomation of sensitive humans bitten by these snakes has been reported. Illustrated are two lobules of gland from a watersnake (Natrix cyclopion). H & E. ×62.5.

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The oesophageal lumen of many chelonians, such as this green sea turtle (Chelonia mydas), is heavily keratinized and lacks mucus-secreting goblet cells. These characteristics reflect the scabrous diet of these marine animals. (1) Stratum corneum. (2) Stratum lucidum. (3) Stratum granulosum. (4) Stratum spinosum. (5) Stratum basale. (6) Muscularis externa. H & E. ×12.5.

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The oesophagus of most snakes and many lizards is characterized by its extensive plaiting which permits the oesophagus to stretch to accommodate enormous prey. Illustrated is a cross-section of the oesophagus of a kingsnake (Lampropeltis triangulum). Because of the necessity for abundant lubrication during the swallowing of furry, feathered or scaly prey, the oesophageal lumen is lined by a mucous epithelium composed of simple non-keratinized columnar cells bearing basal nuclei. H & E. ×62.5.

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Whole mount cross-section of the fundic stomach of a small skink (Scincella lateralis). A very thin serosa covers the outermost visceral surface. The gastric wall is composed of an outer external longitudinal muscularis externa (1), a circular muscularis externa, the muscularis mucosa), and immediately beneath is the glandular mucosa (2) which is composed of pink staining granular chief cells and clear cells. The lumen is lined by tall mucus secreting columnar cells. Parietal cells, present in mammalian gastric mucosae, are lacking in amphibians and reptiles. The outermost surface of the stomach is covered by a delicate serosa (3) formed of non-keratinized squamous cells. H & E. ×12.5.

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Gastric mucosa of a boa constrictor (Boa constrictor). The lumen is covered by tall columnar epithelium. The gastric glands consist of only granular, cuboidal, pink staining chief cells (1) with large vesicular nuclei, and pale staining clear cells (2) whose nuclei are dark and basal. Some gastric pits are lined by both cell types. H & E. ×250.

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The colon of some lizards, particularly folivorous species, is a highly modified sacculated organ divided into multiple chambers that are functionally analogous to the hindgut of lagamorphs and some (herbivorous/folivorous) rodents, and the forestomachs of ruminants. Digestion is enhanced because the villous surface of the colon is covered by a highly absorptive columnar mucosa across which nutrients processed from cellulose-digesting micro organisms are assimilated. The elongated villi that cover the surface are supported, and stiffened, by thin cores of smooth muscle. Illustrated is the sacculated colon of a green iguana (Iguana iguana). H & E. ×12.5.

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1.__

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Liver (pig). The heaxagonal liver lobule is delineated by the green strands of the interlobular connective tissue. (1) Central vein. Masson’s trichrome. ×125.

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Liver (ox). (1) Hepatocytes arranged in cords. (2) Sinusoids lined by endothelial cells and macrophages open into (3) the central vein. Safranin/haematoxylin. ×125.

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Portal canal (triad) (sheep). (1) Branch of the bile duct. (2) Hepatic artery. (3) Lymphatic vessel. (4) Hepatic portal vein. (5) Liver cords. (6) Sinusoids. H & E. ×125.

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Liver (dog). The macrophages have taken up the injected carbon and appear as black areas between the cords of hepatocytes. Carbon-injected with H & E counterstain.×125.

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Liver (dog). The hepatocytes lie in anastomosing cords separated by sinusoids lined by macrophages (arrowed). Safranin/haematoxylin after carbon injection. ×250.

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Gall bladder (cow). (1) Tall columnar epithelium lining the lumen. (2) Mucosal folds. (3) Muscularis. (4) Serosa. H & E. ×12.5.

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The liver and pancreas of some fish, amphibians and reptiles are fused or admixed with one another and form a hepatopancreas. Illustrated is a section of such a mixed organ in an axolotl, a neotenic form of the aquatic salamander (Ambystoma maculatum). The hepatocellular tissue is at the bottom of this section; the exocrine pancreatic portion is in the upper right; an islet is in the upper left. H & E. ×250.

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Pancreas (dog). (1) Serous acini of the exocrine pancreas. (2) Interlobular connective tissue. (3) Interlobular duct. (4) Pancreatic islet, the endocrine pancreas. H & E. ×12.5.

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Pancreas (dog). (1) Serous acinus with a centroacinar cell (arrowed). (2) Interlobular connective tissue. (3) Interlobular duct. H & E. ×125.

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Pancreas (dog). (1) Nucleus lies in the basal basophilic cytoplasm of the serous cell. (2) Eosinophilic granules (the secretion) lie in the luminal cytoplasm. H & E. ×250.

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Pancreatic islet. Pancreas (cat). (1) Pale staining endocrine cells form cords associated with capillaries. (2) Exocrine acinus. H & E. ×125.

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Pancreas of a salamander (Amphiuma tridactyla). Exocrine pancreatic cells characterized by their fine granular eosinophilic cytoplasm (on the left) extend a finger-like isthmus into the islet of paler staining endocrine cells bearing dense nuclei (on the right). The islet cells are arranged into nest-like lobules that are separated from each other and from the exocrine tissue by thin strands of connective tissue that support small blood vessels. H & E. ×250.

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The splenopancreas of a milksnake (Lampropeltis triangulum). The spleen is on the right, a large aggregate of islet tissue is in the middle and a portion of the exocrine pancreatic tissue is on the left. The islet displays hyalinization. H & E. ×125.

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The pancreas of some snakes, particularly many pythons, is characterized by possessing endocrine cells formed into giant islets (often found at the edge of the lobule) rather than into many small nests of cells scattered randomly throughout the parenchyma. Illustrated is a section of the pancreas from a regal (ball) python (Python regius). H & E. ×125.

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Crop (bird). (1) Stratified squamous non-keratinized epithelium. (2) Lamina propria. (3) Muscularis mucosae. (4) Muscularis externa. H & E. ×12.5.

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Proventriculus (bird). (1) Simple columnar mucus-secreting epithelium. (2) Lamina propria. (3) Submucosal glands. (4) Muscularis externa. H & E. ×62.5.

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Proventriculus (bird). (1) Simple columnar mucus secreting epithelium. (2) Lamina propria. (3) Submucosal glands. (4) Muscularis externa. Masson’s trichrome. ×25

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Proventriculus (bird). The submucosal gland lobules are separated by thin strands of connective tissue. Masson’s trichrome. ×250.

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Ventriculus, gizzard (bird). (1) Cornified lining. (2) Epithelium lining the gizzard. (3) Mucosal glands. (4) Lamina propria. H & E. ×25.

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Ventriculus, gizzard (bird). (1) Cornified lining. (2) Lining epithelium. (3) Mucosal glands. H & E. ×125.

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Duodenum (bird). (1) Simple columnar epithelium. (2) Intestinal mucosal glands. (3) Connective tissue core of the villus. (4) Muscularis mucosae. H & E. ×62.5.

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Duodenum (bird). The simple columnar epithelium lining the duodenum has a striated border to allow absorption and goblet cells. Masson’s trichrome. ×125.

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Duodenum (bird). The simple columnar epithelium rests on a lamina propria with numerous lymphatic cells. Masson’s trichrome. ×250.

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Caecum (bird). (1) Lumen of the caecum. (2) Mucosa consists of a columnar epithelium and a lamina propria with extensive deposits of lymphatic tissue. (3) Muscularis. (4) Lumen of the duodenum. Masson’s trichrome. ×12.5.

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Caecum (bird). Dense masses of lymphatic tissue fills the lamina propria. H & E. ×12.5.

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Rectum (bird). The lining epithelium is simple columnar with goblet cells extending into the simple tubular mucosal glands (arrowed). H& E. ×62.5.

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Cloaca (bird). (1) Simple columnar lining epithelium. (2) Simple tubular glands. (3) Lamina propria with lymphatic tissue. (4) Muscularis mucosae. (5) Muscularis externa. Alcian blue/PAS. ×62.5.

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Pancreas (bird). (1) Serous units of the exocrine gland. (2) Pancreatic islet, the endocrine gland. H & E. ×125.