GIT1 GASTROINTESTINAL TRACT1 This resource is licensed under

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GIT-1 (GASTROINTESTINAL TRACT-1) This resource is licensed under the Creative Commons Attribution Non-Commercial &

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

Objectives You should appreciate how the composition of different tissue layers changes along the

Objectives You should appreciate how the composition of different tissue layers changes along the length of the gastrointestinal tract reflecting structural adaptation for function. 1. Recognise and describe a section of oesophagus by identifying layers and their cellular components. 2. 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. 3. Recognise and describe a section of the small intestine by appreciating the differences observed in this part of the gastrointestinal tract. 4. Recognise and describe a section of the large intestine. 5. Recognise and describe a section of the recto-anal junction by observing the marked changes in this area.

SLIDE 28 Oesophagus (dog) Longitudinal section of oesophagus seen at low magnification. Name the

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). 1. 0 mm * Pars laryngea pharyngis

SLIDE 28 Oesophagus (dog) Name the four layers: 1: mucosa. 2: submucosa. 3: tunica

SLIDE 28 Oesophagus (dog) Name the four layers: 1: mucosa. 2: submucosa. 3: tunica muscularis. 4: serosa or adventitia. 1. 0 mm mucosa submucosa (with glands) tunica muscularis serosa or adventitia

SLIDE 28 Oesophagus (dog) How is the tunica muscularis subdivided further? Tunica muscularis consists

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

SLIDE 28 Oesophagus (dog) How is the tunica muscularis subdivided further? Tunica muscularis consists

SLIDE 28 Oesophagus (dog) 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. 2 1 25 µm 250 µm

SLIDE 28 Oesophagus (dog) How is the mucosal layer subdivided further? The mucosal layer

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

SLIDE 28 Oesophagus (dog) How is the mucosal layer subdivided further? The mucosal layer

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

SLIDE 62 Oesophagus (rat) Transverse section of oesophagus seen at low magnification. Make sure

SLIDE 62 Oesophagus (rat) Transverse section of oesophagus seen at low magnification. Make sure you can identify the other main structures on this slide. dorsal 250 µm 1. 0 mm

SLIDE 62 Oesophagus (rat) Transverse section of oesophagus seen at low magnification. Make sure

SLIDE 62 Oesophagus (rat) Transverse section of oesophagus seen at low magnification. Make sure you can identify the other main structures on this slide. dorsal A : oesophagus. B : trachea. C : thyroid gland. D : skeletal muscle. A C 250 µm B C D 1. 0 mm lumen

SLIDE 62 Oesophagus (rat) As with slide 28 identify the four zones in this

SLIDE 62 Oesophagus (rat) As with slide 28 identify the four zones in this transverse section. x 1 100 µm 50 µm

SLIDE 62 Oesophagus (rat) As with slide 28 identify the four zones in this

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

SLIDE 62 Oesophagus (rat) What differences are there between sections 28 Dog oesophagus and

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

SLIDE 62 Oesophagus (rat) What differences are there between sections 28 Dog oesophagus and

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

Oesophagus some species differences Mucosal layer : epithelium : stratified squamous epithelium. (variable degree

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.

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) Low magnification view of whole section. Identify oesophageal

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) Low magnification view of whole section. Identify oesophageal and stomach regions. 1. 0 mm

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) Low magnification view of whole section. Identify oesophageal

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) Low magnification view of whole section. Identify oesophageal and stomach regions. opening of oesophagus into stomach lumen of oesophagus 1. 0 mm

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) What is the most obvious change at this

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) What is the most obvious change at this junction? opening of oesophagus into stomach lumen of oesophagus 1. 0 mm

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) What is the most obvious change at this

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) 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). lumen of stomach lumen of oesophagus 1. 0 mm

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) Area from previous picture. gastric glands columnar epithelium

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

SLIDE 47 Gastro-oesophageal junction H&E (rabbit) A higher magnification view of the sudden change

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

SLIDE 32 Gastro-oesophageal junction PAS (rabbit) The three following pictures are from the same

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

SLIDE 32 Gastro-oesophageal junction PAS (rabbit) The three following pictures are from the same

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). PAS staining is used to demonstrate muco- and glycoproteins in the gastric mucosa. oesophagus stomach 1. 0 mm

SLIDE 32 Gastro-oesophageal junction PAS (rabbit) A continuous secretion of mucous is produced by

SLIDE 32 Gastro-oesophageal junction PAS (rabbit) 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. stomach oesophagus 250 µm

SLIDE 32 Gastro-oesophageal junction PAS (rabbit) Seen here is an area of gastric pits.

SLIDE 32 Gastro-oesophageal junction PAS (rabbit) 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. opening of gastric pit to stomach PAS positive mucous tubular glands 50 µm

Cranial Abdomen - Dog • Cadaver in right lateral recumbency. Abdominal wall has been

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

SLIDE 33 Pyloric region of glandular stomach (dog) Identify the main layers of the

SLIDE 33 Pyloric region of glandular stomach (dog) Identify the main layers of the stomach. 1. 0 mm

SLIDE 33 Pyloric region of glandular stomach (dog) Identify the main layers of the

SLIDE 33 Pyloric region of glandular stomach (dog) 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 4 th layer, the serosa, is not shown. submucosa tunica muscularis split in tissue (artefact) lumen 1. 0 mm

SLIDE 33 Pyloric region of glandular stomach (dog) Identify : deep gastric pits coiled

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

SLIDE 33 Pyloric region of glandular stomach (dog) Identify : deep gastric pits coiled

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

SLIDE 33 Pyloric region of glandular stomach (dog) What type of epithelium lines this

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

SLIDE 33 Pyloric region of glandular stomach (dog) What type of epithelium lines this

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

SLIDE 34 Fundic region of glandular stomach (cat) In this area of fundic stomach

SLIDE 34 Fundic region of glandular stomach (cat) In this area of fundic stomach again identify the four main layers. 1. 0 mm

SLIDE 34 Fundic region of glandular stomach (cat) In this area of fundic stomach

SLIDE 34 Fundic region of glandular stomach (cat) 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. mucosa submucosa tunica muscularis serosa 1. 0 mm

SLIDE 34 Fundic region of glandular stomach (cat) Examine the layer of the lamina

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

SLIDE 34 Fundic region of glandular stomach (cat) Examine the layer of the lamina

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

SLIDE 34 Fundic region of glandular stomach (cat) Identify the tunica muscularis (smooth muscle)

SLIDE 34 Fundic region of glandular stomach (cat) Identify the tunica muscularis (smooth muscle) and the outer serosa. 1. 0 mm 100 µm

SLIDE 34 Fundic region of glandular stomach (cat) Identify the tunica muscularis (smooth muscle)

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

SLIDE 34 Fundic region of glandular stomach (cat) Examine the mucosal layer. What epithelium

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

SLIDE 34 Fundic region of glandular stomach (cat) Examine the mucosal layer. What epithelium

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

SLIDE 34 Fundic region of glandular stomach (cat) Identify : Parietal cells… larger pyramid

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

SLIDE 34 Fundic region of glandular stomach (cat) Identify : Parietal cells Chief cells

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

SLIDE 34 Fundic region of glandular stomach (cat) What do : Parietal cells secrete?

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

SLIDE 34 Fundic region of glandular stomach (cat) What do : Parietal cells secrete?

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

Comparing the pyloric and fundic regions of the stomach. Both are lined by columnar

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?

Comparing the pyloric and fundic regions of the stomach. Both are lined by columnar

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? 1. 2. Presence of gastric pits and glands. Thick muscularis.

SLIDE 44 Gastro-duodenal junction (PAS stain) What are the major changes observed at this

SLIDE 44 Gastro-duodenal junction (PAS stain) What are the major changes observed at this junction? 1. 0 mm

SLIDE 44 Gastro-duodenal junction (PAS stain) What are the major changes observed at this

SLIDE 44 Gastro-duodenal junction (PAS stain) 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. stomach with gastric pits duodenum with villi mucosal glands Brunner’s glands thick muscularis of stomach serosa 1. 0 mm thinner muscularis of duodenum

SLIDE 44 Gastro-duodenal junction (PAS stain) A : gastric pits can be seen, glands

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. A 250 µm B

SLIDE 44 Gastro-duodenal junction (PAS stain) A : gastric pits can be seen, glands

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. L : lymphoid tissue villi M : lamina muscularis Br : Brunner’s glands Cr : crypts gastric pits Cr L M L Br M A 250 µm B

SLIDE 44 Gastro-duodenal junction (PAS stain) At higher magnification. Note the lamina muscularis passes

SLIDE 44 Gastro-duodenal junction (PAS stain) At higher magnification. Note the lamina muscularis passes below the mucosal gland layer of the stomach in A; but in the duodenum B separates the mucosal duodenal crypt glands and the submucosal Brunner’s glands. A 100 µm B

SLIDE 44 Gastro-duodenal junction (PAS stain) At higher magnification. Note the lamina muscularis passes

SLIDE 44 Gastro-duodenal junction (PAS stain) At higher magnification. Note the lamina muscularis passes below the mucosal gland layer of the stomach in A; but in the duodenum B separates the mucosal duodenal crypt glands and the submucosal Brunner’s glands. A : Stomach B : Duodenum M : lamina muscularis duodenal crypts M M Brunner’s glands mucosal glands A submucosa M M submucosa 100 µm B

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa tunica

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa tunica muscularis 0. 5 mm serosa

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa tunica

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa tunica muscularis serosa 0. 5 mm

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa villi

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa villi crypts tunica muscularis serosa In the mucosal layer identify : mucosa submucosa tunica muscularis serosa 0. 5 mm

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa villi

SLIDE 45 Caudal duodenum (cat) Identify the four main layers : mucosa submucosa villi crypts tunica muscularis serosa In the mucosal layer identify : villi mucosa crypts submucosa tunica muscularis serosa 0. 5 mm

SLIDE 45 Caudal duodenum (cat) The mucosal layer of the duodenum. Submucosal Brunner’s glands

SLIDE 45 Caudal duodenum (cat) The mucosal layer of the duodenum. Submucosal Brunner’s glands are absent here in the caudal duodenum, but can be seen in the more proximal portion see previous slide 44. villi crypts (of Lieberkühn) lamina muscularis submucosa 100 µm

SLIDE 45 Caudal duodenum (cat) How does the orientation of the smooth muscle differ

SLIDE 45 Caudal duodenum (cat) How does the orientation of the smooth muscle differ in the two layers of the tunica muscularis? 250 µm

SLIDE 45 Caudal duodenum (cat) How does the orientation of the smooth muscle differ

SLIDE 45 Caudal duodenum (cat) How does the orientation of the smooth muscle differ in the two layers of the tunica muscularis? Outer longitudinal, Inner circular. lamina muscularis submucosa (loose connective tissue) inner circular tunica muscularis outer longitudinal serosa 250 µm

SLIDE 45 Caudal duodenum (cat) details from villi What type of epithelium covers the

SLIDE 45 Caudal duodenum (cat) details from villi What type of epithelium covers the duodenal surface? 50 µm 25 µm

SLIDE 45 Caudal duodenum (cat) details from villi What type of epithelium covers the

SLIDE 45 Caudal duodenum (cat) details from villi What type of epithelium covers the duodenal surface? Columnar. lymphocytes striated border of microvilli lacteal of villus goblet cell 50 µm 25 µm

SLIDE 45 Caudal duodenum (cat) details from villi Why is this epithelium best suited

SLIDE 45 Caudal duodenum (cat) details from villi Why is this epithelium best suited here? lymphocytes striated border of microvilli lacteal of villus goblet cell 50 µm 25 µm

SLIDE 45 Caudal duodenum (cat) details from villi Why is this epithelium best suited

SLIDE 45 Caudal duodenum (cat) details from villi Why is this epithelium best suited here? For its absorptive function. lymphocytes striated border of microvilli lacteal of villus goblet cell 50 µm 25 µm

Duodenum transmission electron micrographs How is the epithelial surface specialised to increase the surface

Duodenum transmission electron micrographs How is the epithelial surface specialised to increase the surface area further? 0. 2 µm 0. 5 µm

Duodenum transmission electron micrographs How is the epithelial surface specialised to increase the surface

Duodenum transmission electron micrographs How is the epithelial surface specialised to increase the surface area further? Striated border of microvilli (brush border). M : mitochondrion. T : tight junction (separates the lumen from the intercellular space). microvilli 0. 2 µm striated or brush border 0. 5 µm

Duodenum transmission electron micrographs The glycocalyx: Is a layer of oligosaccharides found on the

Duodenum transmission electron micrographs The glycocalyx: Is a layer of oligosaccharides found on the cell membrane’s extracellular surface. Associated with absorption it is especially well developed on the microvilli of the duodenum. This sample was treated with ruthenium red, during fixation, to illustrate this glycocalyx. microvilli showing well developed glycocalyx 0. 2 µm

R B L Pancreas left lobe ascending duodenum Pancreas right lobe descending duodenum Duodenum

R B L Pancreas left lobe ascending duodenum Pancreas right lobe descending duodenum Duodenum – Dog ▪ Organ in situ. Cadaver in left lateral recumbency. ▪ Identify also : jejunum & mesojejunum, liver, portal vein, diaphragm. Duodenum – Sheep ▪ Organ in situ. Cadaver in left lateral recumbency. ▪ Identify : Sigmoid loop of duodenum, descending duodenum, ascending duodenum, ▪ Identify also : right kidney, caudate process of liver, portal vein. ▪ L – Left lobe B – Body R – Right lobe of pancreas

Jejenum - Dog • Note: Mesojejenum, blood vessels therein & segmental supply to jejunum.

Jejenum - Dog • Note: Mesojejenum, blood vessels therein & segmental supply to jejunum. • Which major artery supplies the jejunum ?

SLIDE 26 Colon (fox) Transverse view through whole section of fox colon. 1. 0

SLIDE 26 Colon (fox) Transverse view through whole section of fox colon. 1. 0 mm

SLIDE 26 Colon (fox) Identify the main regions of the colon. How does the

SLIDE 26 Colon (fox) Identify the main regions of the colon. How does the colon differ from the small intestine? 0. 5 mm

SLIDE 26 Colon (fox) Identify the main regions of the colon. How does the

SLIDE 26 Colon (fox) Identify the main regions of the colon. How does the colon differ from the small intestine? No villi; much straighter mucosal glands. lymphatic nodule serosa tunica muscularis submucosa lumen 0. 5 mm

SLIDE 26 Colon (fox) Lymphatic nodule in the submucosa. 50 µm 250 µm

SLIDE 26 Colon (fox) Lymphatic nodule in the submucosa. 50 µm 250 µm

SLIDE 26 Colon (fox) Lymphatic nodule in the submucosa. lamina muscularis submucosa tunica muscularis

SLIDE 26 Colon (fox) Lymphatic nodule in the submucosa. lamina muscularis submucosa tunica muscularis lymphocytes lymphatic nodule mucosal glands 50 µm 250 µm

SLIDE 26 Colon (fox) The mucosal layer of the colon. Identify : lumen, epithelium,

SLIDE 26 Colon (fox) The mucosal layer of the colon. Identify : lumen, epithelium, mucosal glands in lamina propria and lamina muscularis. Note the rich blood supply to the underlying submucosa. 250 µm

SLIDE 26 Colon (fox) The mucosal layer of the colon. Identify : lumen, epithelium,

SLIDE 26 Colon (fox) The mucosal layer of the colon. Identify : lumen, epithelium, mucosal glands in lamina propria and lamina muscularis. Note the rich blood supply to the underlying submucosa. lumen epithelium mucosal glands in lamina propria lamina muscularis submucosa blood vessels 250 µm

SLIDE 26 Colon (fox) The long, straight mucosal glands of the colon. Identify mucous

SLIDE 26 Colon (fox) The long, straight mucosal glands of the colon. Identify mucous secreting cells in these glands. 50 µm

SLIDE 26 Colon (fox) The long, straight mucosal glands of the colon. Identify mucous

SLIDE 26 Colon (fox) The long, straight mucosal glands of the colon. Identify mucous secreting cells in these glands. smooth muscle of lamina muscularis some pale staining mucous cells arrowed 50 µm

SLIDE 25 Colon (rabbit) Transverse section through the colon of a rabbit. 1. 0

SLIDE 25 Colon (rabbit) Transverse section through the colon of a rabbit. 1. 0 mm

SLIDE 25 Colon (rabbit) Transverse section through the colon of a rabbit. 1. 0

SLIDE 25 Colon (rabbit) Transverse section through the colon of a rabbit. 1. 0 mm

SLIDE 25 Colon (rabbit) Again identify the four main areas across this section of

SLIDE 25 Colon (rabbit) Again identify the four main areas across this section of colon. 0. 5 mm

SLIDE 25 Colon (rabbit) Again identify the four main areas across this section of

SLIDE 25 Colon (rabbit) Again identify the four main areas across this section of colon. serosa (not clear) tunica muscularis submucosa lumen 0. 5 mm

SLIDE 25 Colon (rabbit) Note the submucosa in this area is very reduced in

SLIDE 25 Colon (rabbit) Note the submucosa in this area is very reduced in thickness. Again, long straight mucosal glands can be identified. 250 µm

SLIDE 25 Colon (rabbit) Note the submucosa in this area is very reduced in

SLIDE 25 Colon (rabbit) Note the submucosa in this area is very reduced in thickness. Again, long straight mucosal glands can be identified. lamina muscularis serosa tunica muscularis submucosal glands packing lamina propria 250 µm lumen

SLIDE 25 Colon (rabbit) Note the submucosa in this area is very reduced in

SLIDE 25 Colon (rabbit) Note the submucosa in this area is very reduced in thickness. Again, long straight mucosal glands can be identified. serosa tunica muscularis submucosal glands packing lamina propria 250 µm lumen

SLIDE 25 Colon (rabbit) At higher magnification : Smooth muscle of the lamina muscularis

SLIDE 25 Colon (rabbit) At higher magnification : Smooth muscle of the lamina muscularis and the mucosal glands packing the lamina propria. 50 µm

SLIDE 25 Colon (rabbit) At higher magnification : Smooth muscle of the lamina muscularis

SLIDE 25 Colon (rabbit) At higher magnification : Smooth muscle of the lamina muscularis and the mucosal glands packing the lamina propria. mucosal glands packing lamina propria lamina muscularis 50 µm

SLIDE 25 Colon (rabbit) What epithelium lines this tissue? 50 µm

SLIDE 25 Colon (rabbit) What epithelium lines this tissue? 50 µm

SLIDE 25 Colon (rabbit) What epithelium lines this tissue? Columnar. columnar epithelium 50 µm

SLIDE 25 Colon (rabbit) What epithelium lines this tissue? Columnar. columnar epithelium 50 µm

SLIDE 27 Recto-anal junction Transitional area from the recto-anal junction. What happens to the

SLIDE 27 Recto-anal junction Transitional area from the recto-anal junction. What happens to the muscle layers here? Mucocutaneous junction of anus & vagina - Sheep 1. 0 mm

SLIDE 27 Recto-anal junction Transitional area from the recto-anal junction. What happens to the

SLIDE 27 Recto-anal junction Transitional area from the recto-anal junction. What happens to the muscle layers here? Lamina muscularis and longitudinal layer of tunica muscularis terminate; Inner circular layer of tunica muscularis forms the internal sphincter. The external anal sphincter is formed from skeletal muscle. external sphincter (skeletal muscle) LM LM : longitudinal muscle of tunica muscularis CM : inner circular muscle of tunica muscularis magnification is too low to clearly identify the lamina muscularis CM 1. 0 mm

SLIDE 27 Recto-anal junction Transitional area from the recto-anal junction. What happens to the

SLIDE 27 Recto-anal junction Transitional area from the recto-anal junction. What happens to the muscle layers here? Lamina muscularis and longitudinal layer of tunica muscularis terminate; Inner circular layer of tunica muscularis forms the internal sphincter. The external anal sphincter is formed from skeletal muscle. external sphincter (skeletal muscle) LM LM : longitudinal muscle of tunica muscularis CM : inner circular muscle of tunica muscularis magnification is too low to clearly identify the lamina muscularis CM change of epithelium type 1. 0 mm

SLIDE 27 Recto-anal junction How does the epithelium change here? 250 µm

SLIDE 27 Recto-anal junction How does the epithelium change here? 250 µm

SLIDE 27 Recto-anal junction How does the epithelium change here? Columnar epithelium of the

SLIDE 27 Recto-anal junction How does the epithelium change here? Columnar epithelium of the rectum changes to stratified squamous non-keratinised epithelium then to keratinised stratified squamous epithelium more distally in the anal canal. stratified squamous columnar 250 µm

SLIDE 27 Recto-anal junction What type of muscle constitutes the external anal sphincter? (not

SLIDE 27 Recto-anal junction What type of muscle constitutes the external anal sphincter? (not shown on this section) 250 µm

SLIDE 27 Recto-anal junction What type of muscle constitutes the external anal sphincter? (not

SLIDE 27 Recto-anal junction What type of muscle constitutes the external anal sphincter? (not shown on this section) Skeletal muscle. anal glands epithelium stratified squamous but now keratinised 250 µm

SLIDE 27 Recto-anal junction What types of gland are associated with the anal sphincter?

SLIDE 27 Recto-anal junction What types of gland are associated with the anal sphincter? 100 µm

SLIDE 27 Recto-anal junction What types of gland are associated with the anal sphincter?

SLIDE 27 Recto-anal junction What types of gland are associated with the anal sphincter? Sebaceous and apocrine sweat glands. gland opening anal glands keratinised stratified squamous epithelium 100 µm

Lectures. Dr Tej Dhoot. Second Year Histology. 017. GIT-1. J Bredl. 13 -07 -04.

Lectures. Dr Tej Dhoot. Second Year Histology. 017. GIT-1. J Bredl. 13 -07 -04. Gross Anatomy Correlates. Dr S Frean. Slides and Stains. Tanya Hopcroft. Compressed version updated. 2006/7. 2010