1. Digestive System 1
Dr. Zahiri

2. Pharynx
Pharynx is a transitional zone between oral cavity and esophagus and trachea
It is lined by stratified squamous nonkeratinized epithelium with submucosal glands
Pharynx has thin lamina propria
In more caudal areas, epithelium may be pseudostratified columnar ciliated with goblet cells
Dr. Maria Zahiri

3. Digestive Tract Digestive tract is consists of: Oral cavity Esophagus
Stomach
Small Intestine
Large Intestine
Rectum
Anus
Dr. Maria Zahiri

4. Common Structure of Digestive Tract
Digestive tract is a hollow tube of varying diameter with wall made up of 4 layers
Mucosa
Submucosa
Muscularis externa
Serosa or adventitia
Dr. Maria Zahiri

5. Mucosa Epithelial lining Lamina propria
Stomach to colon is simple columnar
Other areas are mostly stratified squamous
Lamina propria
is a loose connective tissue with blood and lymphatic vessels, glands and lymphoid nodules
Muscularis mucosa
is composed of an inner circular layer and an outer longitudinal layer of smooth muscle
Dr. Maria Zahiri

6. Submucosa
Submucosa composed of dense irregular fibroelastic connective tissue with many blood and lymphatic vessels
It may have nerve plexus known as Meissner’s submucosal plexus
It may contain glands and lymphoid nodules
Dr. Maria Zahiri

7. Muscularis Externa
Inner circular layer and Outer longitudinal layer of smooth muscle cells
Stomach has inner oblique layer in addition to the other 2 layers
Myenteric (Auerbach’s) plexus made up of millions of neurons lies between smooth muscle layers
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8. Serosa or Adventitia
Both serosa and adventitia are composed of loose connective tissue rich in blood and lymphatic vessels
Adipose tissue often is plentiful
Simple squamous layer of mesothelium presented when an organ is intraperitoneal and it is known as serosa
Dr. Maria Zahiri

9. Functions of Epithelium in Digestive Tract
It acts as a permeability barrier between gut lumen and blood
Transport and digest food
Secretes different types of enzymes
Absorb nutrients
Produce and secrete hormones involved in digestion
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11. Esophagus
Mucosa:
has a thick stratified squamous nonkeratinized epithelium
Mucous glands known as esophageal cardiac glands are plentiful in lamina propria near the junction with stomach (cardia) and pharynx
Muscularis mucosa is unusual consists of a single layer of longitudinally oriented smooth muscle cells
Submucosa houses mucous glands known as esophageal glands proper, that are tubuloacinar glands with mucous and serous cells
Dr. Maria Zahiri

12. Esophagous
Muscularis externa in upper esophagus has only skeletal muscle fibers
Middle esophagus has a mixture of skeletal and smooth muscle cells
Lower esophagus has only smooth muscle cells
Adventitia covers esophagus until it pierce the diaphragm, after which it is replaced by a serosa
At the junction of the esophagus with the stomach:
change in the epithelial lining from the stratified squamous epithelium to the simple columnar epithelium
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14. Gastroesophageal Reflux Disease (GERD)
Normal histology of the esophagus
Histology from a patient with reflux esophagitis.
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15. Stomach
Stomach has 4 regions known as cardia, fundus, body, and pylorus
fundus and body are identical histologically
Thick muscle layers grind and mix food
Secretions of enzymes and acid begin digestion
Gastric wall is highly folded display rugae
Dr. Maria Zahiri

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17. Stomach Mucosa Surface epithelium
is simple columnar mucous producing cells
(does not change throughout the stomach)
Produce Alkalin sheat (mucus) against acidic contents of the stomach
gastric pits: Surface epithelium invaginates into lamina propria
Gastric glands open at the base of pits
Cardiac, fundic and pyloric glands differ from each other
Lamina propria composed of loose CT with smooth muscle and lymphocytes and occupied mainly by glands
Muscularis mucosa consists of inner circular and outer longitudinal smooth muscle layers
Dr. Maria Zahiri

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20. Gastric Pits and Epithelial lining
Simple columnar epithelium of mucus producing cells
Cells have a height about µm
An oval nucleus located in basal cytoplasm
Many mucus granules aggregate in apical cytoplasm
Thick mucus layer known as visible mucus protects stomach epithelium from autodigestion
Junctional complexes at lateral surface attach cells together
Regenerative cells are presented at the base of these pits but are numerous in the neck of the glands
Dr. Maria Zahiri

21. peptic ulcer, also known as peptic ulcer disease (PUD)
is a distinct breach in the mucosa of the stomach as a result of caustic effects of acid and pepsin in the lumen.
Histologically, peptic ulcer is identified as necrosis of the mucosa which produces lesions .
It is the most common ulcer of an area of the gastrointestinal tract that is usually acidic and thus extremely painful. Helicobacter pylori is one of the most common causes of peptic ulcer.
Ulcers can also be caused or worsened by
drugs such as aspirin, ibuprofen, and other
NSAIDs (Nonsteroidal anti-inflammatory
drugs), ethanol.
Dr. Maria Zahiri

22. Cells of Gastric Gland There is 6 different cell types:
Surface lining cells
Mucous neck cells
Regenerative (stem) cells
Parietal cells
Chief (Zymogenic) cells
DNES (APUD or Entroendocrine cells)
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23. Cardiac Region
Cardiac region is a narrow band cm in width, at the gastroesophageal junction
It has simple or branched tubular cardiac glands with large lumen at terminus
Glands are shallow, slightly coiled
Composed mostly of:
surface lining and mucous neck cells
a few parietal and DNES cells
no chief cells
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24. Fundus and Body
Gastric pits are narrow and shallow in fundus and body of the stomach
Glands are long and straight
Many parietal and chief cells are in glands
Neck of gland has undifferentiated cells and
mucous cells
Base of glands have parietal cells, chief cells
and enteroendocrine cells
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25. Cells of the Fundus Undifferentiated cells:
are narrow columnar cells that located in neck of gland
have oval basal nuclei, distinct nucleolus, mitotic figures
stem cells
surface cells survive 3-7 days and replaced by these cells
Dr. Maria Zahiri

26. have a basal irregular nuclei
Mucous neck cells:
have a basal irregular nuclei
mucous granules, this mucus is soluble and lubricate the gastric contents
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27. Parietal ( oxyntic) cells: located in upper half of glands
have eosinophilic cytoplasm and many mitochondria.
Produce HCl and intrinsic factor
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28. In EM: Intracellular canaliculi and a tubulovesivular system are prominent features of this cell
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30. Chief cells (zymogenic) located in deeper portion of the glands
They are basophilic due to many ribosomes
Produce pepsinogen, renin, gastric lipase and serous
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31. Pernicious anemia (also known as Addison's anemia)
atrophic gastritis or autoimmune destruction of gastric parietal cells
loss of gastric parietal cells secretion of intrinsic factor
absorption of vitamin B12 in the ileum
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33. manufacture endocrine, paracrine, and neurocrine hormone
Enteroendocrine cells "argetaffin cells" ("silver affinity"), APUD (Amine Precursor Uptake & Decarboxylase )
manufacture endocrine, paracrine, and neurocrine hormone
Located in the base of glands, in light microscopy appear as clear cell
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34. Pylorus
Pylorus has deep and open gastric pits with short coiled glands
Mucous neck cells are most predominant which produce mucous and lysozyme
Parietal cells and DNES are few
G cells Gastrin parietal cell HCl output
D cells somatostatin
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35. Stomach Submucosa
Submucosa is composed of irregular collagenous connective tissue
Contains blood and lymphatic vessels
Lymphoid and mast cells and other cells like CT proper are located in submucosa
Submucosal plexus is near muscularis externa
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36. Stomach Muscularis Externa
Muscularis Externa has 3 layers
Internal oblique layer is not well defined except at cardiac region
Middle is circular layer (forms pyloric sphincter)
Outer longitudinal layer pronounced at cardiac region and body
The myenteric plexus is located between the middle and outer layers
Serosa
Serosa composed of a thin layer of loose CT with covering of wet simple squamous mesothelium
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37. Small Intestine
Small Intestine functions in completion of digestion and absorption of nutrients
It has 3 segments: duodenum, jejunum, and ileum
The surface area of intestine is enlarged by the formation of plicae circularis (Kerckring valve), villi, microvilli, and crypts of Lieberkuhn
Villi of lamina propria are leaf-shaped in duodenum, finger- shaped in ileum and jejunum
Dr. Maria Zahiri

38. Small Intestine
At the base of villi are simple tubular glands known as crypts of Lieberkuhn
Crypts have the following cells:
Regenerative cells (stem cells)
Absorptive cells
Goblet cells
Paneth cells
M cells
Entroendocrine cells
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40. Absorptive Cells (enterocytes)
are tall columnar cells with oval basal nucleus and rich in organelles (RER,SER, GA, endosomes)
Apical surface has many microvilli that form striated border
Each cell has about 3000 microvilli for increased surface area covered by a thick glycocalyx layer which have enzymatic components
Lateral cell membrane form junctional complexes
These cells function in terminal digestion and absorption
Disacharidase & proteinase
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41. Goblet Cells are Few in duodenum but many in ileum
Unicellular glands that produce mucinogen whose hydrated form is mucin a component of mucus
It acts to protect and lubricate epithelium
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42. Regenerative cells
Regenerative cells are stem cells that proliferate to repopulate the other cells
Their rate of division is high
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43. Paneth Cells Paneth Cells are located in basal area of gland
They are exocrine serous, eosinophilic granules containing lysozyme
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44. Microfold Cells
Microfold Cells are specialized epithelial cells which are covering lymphoid follicles of Peyer’s patches
They are cuboidal cells that can phagocytose antigens
and transport them to underlying immune cells
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45. Entroendocrine Cells These are Pale cells with small granules
Constitute about 1% of the cells covering villi and intervillar surface
Produce paracrine and endocrine hormones
These hormones include: glucagon,
gastrin, secretin, gastric inhibitory peptide,
cholecystokinin, somatostatin, motilin,
serotonin, substance P, vasoactive
intestinal peptide
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47. Subepithelial Tissues
Lamina propria is composed of loose connective tissue with blood and lymph vessels, nerves, smooth muscle, lymphoid cells and macrophages
Lamina propria form core of the villi
Muscularis mucosae is typical and enter the villus and extended through its core
Submucosa is composed of dense irregular fibroelastic CT
Duodenum has Brunner’s glands (mucous glands)
Peyer’s patches mostly located in ileum
Dr. Maria Zahiri

48. Peyer’s patches
Peyer’s patches mostly located in ileum; there is about 30 patches that are composed of lymphoid nodules; usual epithelium is replaced by M-cells
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49. Brunner’s gland
Brunner’s gland are branched, tubuloalveolar glands whose secretory portions resemble mucous acini
Ducts of them usually pierce the base of the crypts of Libeberkuhn
Secrete a mucus, alkaline fluid, and Urogastrone
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50. Enteric Nervous System
Enteric Nervous System is consists of Auerbach’s plexus and Meissner's plexus
Neurons of Auerbach’s plexus located between layers of the muscularis externa
Submucosal (Meissner's) plexus innervates submucosa (parasympathetic)
Parasympathetic fibers increase gut activity
Sympathetic adrenergic fibers decrease gut activity
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51. Large Intestine(Colon)
Mucosa of large intestine has folds except in rectum
Colon has no villi
Epithelium is columnar with short microvilli
The absorptive cells are the most numerous cell type
Glands of Lieberkuhn contain goblet cells and a few endocrine cells but there is not any paneth cells
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52. Large Intestine(Colon)
Functions of epithelium include water absorption, mucous production and feces formation
Lamina propria has lymphoid cells and some nodules
An increment in bacterial population
Muscularis externa has typical circular layer; longitudinal layer forms 3 bands known as the taeniae coli
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55. Appendix Appendix is an evagination of large intestine
It has a narrow lumen with abundant lymphoid follicles in submucosa, and lamina propria
Its Structure is similar to large intestine but has many more DNES cells
It has not any teniae coli
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56. Rectum
Rectum resembles the colon but the crypts of Lieberkühn are deeper and fewer
The mucosa contains numerous goblet cells
The muscularis externa has both inner circular and outer longitudinal smooth muscle layers, no teniae coli
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57. Anal Canal
In anal canal the crypts are short and few and in distal half there is no crypts
Mucosa has longitudinal folds, the anal columns (rectal columns of Morgagni)
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59. Anal Canal
Epithelium is simple cuboidal from rectum to pectinate line, and stratified squamus nonkeratinaized from pectinate line to the external anal orifice
At the anus epithelium changes to epidermis
Lamina propria houses anal glands (at rectoanal junction) and circumanal glands (at distal end)
Submucosa has plexus of large veins, if these become varicose they can become hemorrhoids
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60. Anal Canal
Muscularis externa consists of inner circular and outer longitudinal smooth muscle cells
Inner circular layer thickened and form the internal anal sphincter
External anal sphincter forms by skeletal muscles of floor of pelvis
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62. روزگارتان پر از خیر
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