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GIT-1 ( GASTROINTESTINAL TRACT-1)

GIT-1 ( GASTROINTESTINAL TRACT-1). This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License. Objectives.

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GIT-1 ( GASTROINTESTINAL TRACT-1)

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  1. GIT-1(GASTROINTESTINAL TRACT-1) This resource is licensed under the Creative Commons Attribution Non-Commercial & No Derivative Works License

  2. Objectives You should appreciate how the composition of different tissue layers changes along the length of the gastrointestinal tract reflecting structural adaptation for function. Recognise and describe a section of oesophagus by identifying layers and their cellular components. Recognise and describe a section of glandular stomach at both fundic and pyloric regions. You should appreciate the significance of the major changes observed in mucosal and muscle layers in this compartment and be able to distinguish different cell types in gastric glands. Recognise and describe a section of the small intestine by appreciating the differences observed in this part of the gastrointestinal tract. Recognise and describe a section of the large intestine. Recognise and describe a section of the recto-anal junction by observing the marked changes in this area.

  3. 1.0 mm SLIDE 28 Oesophagus (dog) Longitudinal section of oesophagus seen at low magnification. Name the four layers. Oesophagus (proximal) – dog ▪ Dorsal view ▪ Pharynx and proximal oesophagus have been opened dorsally. Window has been cut in trachea. ▪ Identify : papillated (filiform) mucosa of tongue root, epiglottis, arytenoid cartilages & musculature, vestibulum oesophagi* piriform recess* limen pharyngoesophageum* aditus laryngis, thyrohyoid bones, stylohyoid bones (transected). * Pars laryngea pharyngis

  4. SLIDE 28 Oesophagus (dog) 1.0 mm mucosa Name the four layers: 1: mucosa. 2: submucosa. 3: tunica muscularis. 4: serosa or adventitia. submucosa (with glands) tunica muscularis serosa or adventitia

  5. SLIDE 28 Oesophagus (dog) 2 1 2 1 250 µm How is the tunica muscularis subdivided further? Tunica muscularis consists of : 25 µm

  6. How is the tunica muscularis subdivided further? Tunica muscularis consists of : 1. outer longitudinal muscle layer. 2. inner circular muscle layer. In this section of dog oesophagus the tunica muscularis in this region consists of striated muscle. SLIDE 28 Oesophagus (dog) 2 1 2 1 250 µm 25 µm

  7. SLIDE 28 Oesophagus (dog) How is the mucosal layer subdivided further? The mucosal layer consists of : 250 µm

  8. How is the mucosal layer subdivided further? The mucosal layer consists of : 1. epithelium. 2. lamina propria. 3. lamina muscularis. SLIDE 28 Oesophagus (dog) epithelium lamina propria lamina muscularis (smooth muscle) duct from sub mucosal gland 250 µm sub mucosal glands

  9. SLIDE 62 Oesophagus (rat) dorsal 250 µm Transverse section of oesophagus seen at low magnification. Make sure you can identify the other main structures on this slide. 1.0 mm

  10. SLIDE 62 Oesophagus (rat) dorsal A : oesophagus. B : trachea. C : thyroid gland. D : skeletal muscle. A C 250 µm Transverse section of oesophagus seen at low magnification. Make sure you can identify the other main structures on this slide. B C lumen D 1.0 mm

  11. SLIDE 62 Oesophagus (rat) As with slide 28 identify the four zones in this transverse section. x1 50 µm 100 µm

  12. As with slide 28 identify the four zones in this transverse section. • mucosa (epithelium and lamina propria). • submucosa. • tunica muscularis. • serosa or adventitia. SLIDE 62 Oesophagus (rat) lamina propria epithelium 1 As with slide 28 identify the four zones in this transverse section. 2 x1 3 4 50 µm 100 µm

  13. Tunica muscularis (rat) SLIDE 62 Oesophagus (rat) What differences are there between sections 28 Dog oesophagus and 62 Rat oesophagus? 25 µm

  14. What differences are there between sections 28 Dog oesophagus and 62 Rat oesophagus? 28 : Stratified squamous epithelium, non-keratinised. 62 : Stratified squamous epithelium, highly keratinised. 28 : Submucosal mucous glands present. 62 : Absence of glands in submucosa. In both, the tunica muscularis consists of striated muscle. Tunica muscularis (rat) SLIDE 62 Oesophagus (rat) 25 µm

  15. Oesophagus some species differences Mucosal layer : epithelium : stratified squamous epithelium. (variable degree of keratinisation between species). lamina muscularis : may form a complete layer, but often seen as scattered muscle bundles in horses, ruminants and cats. In the dog and pig it is absent in the cranial portion. Submucosa : mucous glands : these tubuloalveolar glands vary in distribution. dogs : along the full length. pigs : in the cranial half, but sparse caudally. cat, horse, ruminant : in the cranial third. Tunica muscularis : dog and ruminant : consists of skeletal muscle along the entire length. horses : the cranial two-thirds is skeletal. cats : the cranial four-fifths is skeletal. pigs : changes from skeletal to smooth muscle just caudal to the diaphragm.

  16. SLIDE 47 Gastro-oesophageal junction H&E (rabbit) Low magnification view of whole section. Identify oesophageal and stomach regions. 1.0 mm

  17. SLIDE 47 Gastro-oesophageal junction H&E (rabbit) opening of oesophagus into stomach lumen of stomach Low magnification view of whole section. Identify oesophageal and stomach regions. lumen of oesophagus 1.0 mm

  18. What is the most obvious change at this junction? SLIDE 47 Gastro-oesophageal junction H&E (rabbit) opening of oesophagus into stomach lumen of stomach lumen of oesophagus 1.0 mm

  19. What is the most obvious change at this junction? Epithelium changes from stratified squamous in the oesophagus to columnar in the stomach. Glands from few or no mucous glands in oesophagus to gastric glands in stomach. Thickening of tunica muscularis in the stomach (cardiac sphincter muscle). SLIDE 47 Gastro-oesophageal junction H&E (rabbit) lumen of stomach lumen of oesophagus 1.0 mm

  20. SLIDE 47 Gastro-oesophageal junction H&E (rabbit) gastric glands columnar epithelium Area from previous picture. stratified squamous epithelium thickened tunica muscularis 250 µm

  21. SLIDE 47 Gastro-oesophageal junction H&E (rabbit) columnar epithelium (stomach) A higher magnification view of the sudden change from stratified squamous epithelium in the oesophagus to a simple columnar epithelium lining the stomach. stratified squamous epithelium (oesophagus) 100 µm

  22. SLIDE 32 Gastro-oesophageal junction PAS (rabbit) The three following pictures are from the same tissue block but have been stained using periodic acid Schiff (PAS). 1.0 mm

  23. SLIDE 32 Gastro-oesophageal junction PAS (rabbit) PAS staining is used to demonstrate muco- and glycoproteins in the gastric mucosa. oesophagus The three following pictures are from the same tissue block but have been stained using periodic acid Schiff (PAS). stomach 1.0 mm

  24. SLIDE 32 Gastro-oesophageal junction PAS (rabbit) stomach oesophagus A continuous secretion of mucous is produced by cells in the epithelial lining of the stomach. Gastric pits open onto the surface of the stomach. Mucous and mucous secreting cells are PAS positive and stain bright red/pink. 250 µm

  25. SLIDE 32 Gastro-oesophageal junction PAS (rabbit) opening of gastric pit to stomach PAS positive mucous Seen here is an area of gastric pits. Branched tubular glands open into these gastric pits. The neck cells of these glands are cuboidal→columnar mucous secreting cells. tubular glands 50 µm

  26. Cranial Abdomen - Dog • Cadaver in right lateral recumbency. Abdominal wall has been removed. Ribcage & diaphragm intact. Left ribcage is retracted laterally with forceps. • Identify: Tendinous & muscular portions of diaphragm, left lateral & left medial lobes of liver, right medial lobe of liver, fundus & body of stomach, greater curvature of stomach & gastrosplenic ligament, spleen. • Also visible: Large intestine & jejunum

  27. SLIDE 33 Pyloric region of glandular stomach (dog) Identify the main layers of the stomach. 1.0 mm

  28. Identify the main layers of the stomach. Mucosa, submucosa, tunica muscularis (very thick layer) and serosa. Due to the large size of this specimen part of the tunica muscularis and the 4th layer, the serosa, is not shown. SLIDE 33 Pyloric region of glandular stomach (dog) submucosa mucosa tunica muscularis split in tissue (artefact) lumen 1.0 mm

  29. SLIDE 33 Pyloric region of glandular stomach (dog) Identify : deep gastric pits coiled glands in lamina propria opening into gastric pits lamina muscularis 250 µm

  30. SLIDE 33 Pyloric region of glandular stomach (dog) M : lamina muscularis C : coiled glands C Identify : deep gastric pits coiled glands in lamina propria opening into gastric pits lamina muscularis gastric pits M 250 µm

  31. SLIDE 33 Pyloric region of glandular stomach (dog) What type of epithelium lines this tissue? 50 µm

  32. SLIDE 33 Pyloric region of glandular stomach (dog) opening of gastric pit simple columnar epithelium What type of epithelium lines this tissue? Columnar. 50 µm

  33. SLIDE 34 Fundic region of glandular stomach (cat) In this area of fundic stomach again identify the four main layers. 1.0 mm

  34. In this area of fundic stomach again identify the four main layers. a). Mucosal layer comprising epithelium, lamina propria and lamina muscularis. b). Submucosa. c). Tunica muscularis. d). Serosa. SLIDE 34 Fundic region of glandular stomach (cat) mucosa submucosa tunica muscularis serosa 1.0 mm

  35. SLIDE 34 Fundic region of glandular stomach (cat) Examine the layer of the lamina muscularis. It is composed of three layers of smooth muscle. 1.0 mm 50 µm

  36. SLIDE 34 Fundic region of glandular stomach (cat) gastric glands blood vessel Examine the layer of the lamina muscularis. It is composed of three layers of smooth muscle. lamina muscularis three layers of smooth muscle submucosa 50 µm

  37. SLIDE 34 Fundic region of glandular stomach (cat) Identify the tunica muscularis (smooth muscle) and the outer serosa. 100 µm 1.0 mm

  38. SLIDE 34 Fundic region of glandular stomach (cat) submucosa Identify the tunica muscularis (smooth muscle) and the outer serosa. inner circular tunica muscularis outer longitudinal serosa 100 µm

  39. SLIDE 34 Fundic region of glandular stomach (cat) Examine the mucosal layer. What epithelium lines this tissue? 25 µm 250 µm

  40. Examine the mucosal layer. What epithelium lines this tissue? Columnar. Note shallower gastric pits here than in the pyloric region. columnar epithelium SLIDE 34 Fundic region of glandular stomach (cat) gastric pits 25 µm 250 µm

  41. SLIDE 34 Fundic region of glandular stomach (cat) Identify : Parietal cells… larger pyramid shaped more abundant in upper part of glands. Chief cells…… basophilic cells, more abundant at the base of the glands. 250 µm 25 µm

  42. SLIDE 34 Fundic region of glandular stomach (cat) most parietal cells in upper gland basophilic chief cells more abundant in deeper areas P Identify : Parietal cells P Chief cells C C P P C 250 µm 25 µm

  43. SLIDE 34 Fundic region of glandular stomach (cat) P : Parietal cells C : Chief cells P What do : Parietal cells secrete? Chief cells secrete? C P P C 25 µm

  44. SLIDE 34 Fundic region of glandular stomach (cat) P : Parietal cells C : Chief cells P What do : Parietal cells secrete? HCl Chief cells secrete? Pepsinogen C P P C 25 µm

  45. Comparing the pyloric and fundic regions of the stomach. Both are lined by columnar epithelium. Pyloric : deeper gastric pits. coiled glands. thick tunica muscularis. Fundic : gastric pits shallow. glands straight. less thick tunica muscularis. abundance of parietal and chief cells in glands. List two histological features that enable you to distinguish the stomach from other compartments of the gastrointestinal tract?

  46. Comparing the pyloric and fundic regions of the stomach. Both are lined by columnar epithelium. Pyloric : deeper gastric pits. coiled glands. thick tunica muscularis. Fundic : gastric pits shallow. glands straight. less thick tunica muscularis. abundance of parietal and chief cells in glands. List two histological features that enable you to distinguish the stomach from other compartments of the gastrointestinal tract? Presence of gastric pits and glands. Thick muscularis.

  47. SLIDE 44 Gastro-duodenal junction (PAS stain) What are the major changes observed at this junction? 1.0 mm

  48. SLIDE 44 Gastro-duodenal junction (PAS stain) stomach with gastric pits duodenum with villi mucosal glands mucosal glands What are the major changes observed at this junction? 1. Gastric pits to villi with striated border. 2. Presence of not only mucosal but also submucosal Brunner’s glands. 3. A reduction in the thickness of the muscularis. Brunner’s glands thick muscularis of stomach thinner muscularis of duodenum serosa 1.0 mm

  49. SLIDE 44 Gastro-duodenal junction (PAS stain) A : gastric pits can be seen, glands found only in the mucosal layer. B : duodenal area with villi. At the base of the villi are the crypts with mucosal glands; deeper in the submucosal layer are Brunner’s glands. B A 250 µm

  50. SLIDE 44 Gastro-duodenal junction (PAS stain) villi M : lamina muscularis Br : Brunner’s glands Cr : crypts gastric pits A : gastric pits can be seen, glands found only in the mucosal layer. B : duodenal area with villi. At the base of the villi are the crypts with mucosal glands; deeper in the submucosal layer are Brunner’s glands. L : lymphoid tissue Cr L M L Br M B A 250 µm

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