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What type of epithelium is found in the lowest part of the esophagus?
Which layer of the esophagus contains mucous glands?
What type of muscle fibers are found in the middle part of the esophagus?
What is the outermost layer of the esophagus in the abdominal part?
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What type of epithelium is found in the mucosa of the cardia of the stomach?
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What type of epithelium is present in the major part of the gastrointestinal tract?
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What are the longitudinal folds of mucosa in the interior of the empty stomach called?
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Which layer of the gastrointestinal tract contains Meissner's plexus of nerves?
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What type of connective tissue is present in the lamina propria?
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Which layer of the gastrointestinal tract is replaced by adventitia in retroperitoneal organs?
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What type of muscle fibers are present in the muscularis mucosa?
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Which plexus of nerves is situated between the two layers of smooth muscle fibers in the muscularis externa?
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What is the approximate proportion of the mucosa's thickness occupied by the gastric pits?
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What is the primary function of the mucus secreted by the cardiac glands?
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What is the layer of the stomach that consists of dense irregular connective tissue and larger blood vessels?
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What is unique about the muscularis externa of the stomach compared to the rest of the GI tract?
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What is the outermost layer of the cardiac stomach?
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What is the layer that lies between the submucosa and the muscularis externa?
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What is the main function of the enterocytes lining the crypts?
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Which type of cells are responsible for replacing other cells in the crypts?
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What is the characteristic feature of the submucosa in the duodenum?
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What is the function of the neuroendocrine cells in the crypts?
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What type of epithelial cells are present in the colon epithelium?
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What is the main component of the core of the villus?
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What is the function of the intestinal glands in the lamina propria?
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What is the characteristic feature of the muscularis mucosa?
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In the histology of the appendix, which layer breaks the muscularis mucosa?
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What is the characteristic of the muscularis mucosa in the appendix?
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What is the characteristic of the submucosa in the appendix?
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Study Notes
Small Intestine
- Core of the villus is formed by connective tissue, blood vessels, and lymph vessels of the lamina propria.
- Villi are covered by simple columnar epithelium (enterocytes) with some goblet cells in between.
- Small intestine lamina propria contains connective tissue, blood vessels, lymph vessels, and intestinal glands (crypts of Lieberkuhn) which open into the lumen between the villi.
- Crypts are mainly lined by simple columnar cells with microvilli (enterocytes) which are absorptive in function.
Small Intestine Lamina Propria
- Contains connective tissue, blood vessels, and lymph vessels, and intestinal glands (crypts of Lieberkuhn) which open into the lumen between the villi.
- Crypts are mainly lined by simple columnar cells with microvilli (enterocytes) which are absorptive in function.
- Other cells lining the crypts include:
- Goblet cells (produce mucin)
- Paneth cells (defensive in function)
- Neuroendocrine cells (produce locally acting hormones that regulate motility and secretion of GIT)
- Stem cells (replace other cells)
- Small intestine lamina propria of ileum contains solitary lymphoid follicles called Peyer’s patches.
Muscularis Mucosa
- Made up of inner circular and outer longitudinal layer of smooth muscle fibers.
- Some of these fibers extend into the core of the villus.
Submucosa
- Contains connective tissue, blood vessels, lymph vessels, and nerve fibers.
- Characterized by the presence of mucous glands (Brunner’s glands) in the duodenum.
- Contains Peyer’s patches (aggregated lymphoid follicles) in the ileum.
Muscularis Externa
- Has outer longitudinal and inner circular layer of smooth muscle fibers.
Esophagus
Histology of Esophagus
- Wall of the esophagus presents 4 layers:
- Mucosa (mucous membrane)
- Submucosa
- Muscularis externa
- Adventitia
- Mucous membrane (mucosa) is the innermost layer and contains 3 parts:
- Epithelium
- Lamina propria
- Muscularis mucosa
- Epithelium is of stratified squamous non-keratinized type, except in the lowest part, which is lined by simple columnar type epithelium.
Lamina Propria
- Made up of loose irregular connective tissue with blood vessels.
- Muscularis mucosa is a thin layer made up of muscle fibers, arranged in 2 layers:
- Inner layer of circularly arranged muscle fibers
- Outer layer of longitudinally arranged muscle fibers
Submucosa
- Contains dense irregular connective tissue, blood vessels, and mucous glands (esophageal glands).
- Larger ducts of the glands extend to the lumen and are lined by stratified columnar epithelium.
- Glands secrete mucus, which aids in the passage of food.
Muscularis Externa
- Made up of thick layer of muscle fibers, arranged in 2 layers:
- Inner layer of circularly arranged muscle fibers
- Outer layer of longitudinally arranged muscle fibers
- Muscularis externa in the upper part of the esophagus is made of skeletal muscle fibers.
- In the lower part, it is made of smooth muscle fibers.
- In the middle part, it is made of both skeletal and smooth muscle fibers.
Adventitia
- Is the outermost layer.
- Made up of loosely arranged connective tissue with blood vessels.
- Adventitia is replaced by serosa in the abdominal part of the esophagus.
Stomach
Histology of Stomach
- Stomach is the most dilated part of the GI tract.
- Stomach has 4 parts – cardia, fundus, body, pyloric part.
- Interior of the empty stomach presents longitudinal folds of mucosa – gastric rugae.
- HISTOLOGY OF CARDIA OF STOMACH:
- Has 4 main layers: the inner mucosa, submucosa, muscularis externa, and outer serosa.
- Mucosa made up of 3 layers (epithelium, lamina propria and muscularis mucosa) of the cardia has a simple columnar epithelium with many invaginations that form millions of gastric pits.
- These layers are similar throughout the length of the digestive tract but there is regional modification and specialization.
Colon
Histology of Colon
- Epithelium (simple columnar with goblet cells)
- Intestinal glands in lamina propria
- Muscularis mucosa
- Submucosa
- Muscularis externa
- Serosa
Appendix
Histology of Appendix
- Mucosa:
- Epithelium: Simple columnar epithelium with lots of goblet cells.
- Lamina propria: Contains aggregation of lymphocytes, which extend into the submucosa breaking muscularis mucosa.
- Also contains few intestinal glands
- Muscularis mucosa: Inner circular and outer longitudinal layer of smooth muscle fibers.
- Submucosa: It is thin with connective tissue, blood vessels, lymph vessels, and nerve fibers.
- Muscularis externa: Has outer longitudinal and inner circular layer of smooth muscles.
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Description
Test your knowledge of the layers of the gastrointestinal tract, including the epithelium, lamina propria, muscularis mucosa, and more. Learn about the structure and function of each layer and how they work together to facilitate digestion. This quiz covers the regional modifications and specializations of the GIT layers.
